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Digital Photography

Digital photography

] ]] Digital photography, as opposed to film photography, uses an electronic sensor to record the image as binary data. This facilitates storage and editing of the images on personal computers. Digital cameras now outsell film cameras and include features not found in film cameras such as the ability to shoot video and record audio. Some other devices, such as mobile phones, now include digital photography features.

History

The first video tape recorder (VTR) was made in 1951 that captured live images from television cameras and saved the information in digital form onto magnetic tapes. Bing Crosby labs pioneered the VTR research, and was put in common use in the television industry. During 1960s, governments took an interest in digital imaging due to its application in spy satellites. Government use of digital technology helped advance the science of digital imaging, however, the private sector also made significant contributions. Texas Instruments patented a film-less electronic camera in 1972, the first to do so. In August, 1981, Sony released the Sony Mavica electronic still camera, the camera which was the first commercial electronic camera. Images were recorded onto a mini disc and then put into a video reader that was connected to a television monitor or color printer. However, the early Mavica cannot be considered a true digital camera even though it started the digital camera revolution. It was a video camera that took video freeze-frames. Kodak took an interest in digital cameras, and since mid-1970s, it invented several solid-state sensors to convert light and pictures directly to digital form. In 1986, Kodak scientists invented the world's first megapixel sensor, capable of recording 1.4 million pixels that could produce a 5x7-inch digital photo-quality print. In 1987, Kodak released seven products for recording, storing, manipulating, transmitting and printing electronic still video images. In 1990, Kodak developed the Photo CD system and proposed "the first worldwide standard for defining color in the digital environment of computers and computer peripherals." In 1991, Kodak released the first professional digital camera system (DCS), aimed at photojournalists. It was a Nikon F-3 camera equipped by Kodak with a 1.3 megapixel sensor. The first digital cameras for the consumer-level market that worked with a home computer via a serial cable were the Apple QuickTake 100 camera (February 17 , 1994), the Kodak DC40 camera (March 28, 1995), the Casio QV-11 (with LCD monitor, late 1995), and Sony's Cyber-Shot Digital Still Camera (1996). However, Kodak entered into an aggressive co-marketing campaign to promote the DC40 and to help introduce the idea of digital photography to the public. Kinko's and Microsoft both collaborated with Kodak to create digital image-making software workstations and kiosks which allowed customers to produce Photo CD Discs and photographs, and add digital images to documents. IBM collaborated with Kodak in making an internet-based network image exchange. Hewlett-Packard was the first company to make color inkjet printers that complemented the new digital camera images.

Sensors

There are two main types of sensors:
- charge-coupled device (CCD) - charge is shifted to a central charge-to-voltage converter
- CMOS sensors There are also two main types of sensor mechanisms possible:
- Area array
- Linear array (in professional "scanning" camera backs) An area array sensor reads the entire image plane at once, whereas a linear array sensor works more like a flatbed scanner. Since this technology predates area arrays, it was available earlier, in professionally-priced studio cameras. With the advent of area array sensors, consumer digital cameras became available for considerably lower prices. (The Ritz Dakota Digital is an extreme example.)

Multifunctionality and connectivity

Except for some linear array type at the highest-end and simple web cams at the lowest-end, a digital memory device (usually flash memory; floppy disks and CD-RWs are less common) is usually used for storing images, which may then be transferred to a computer later. Digital cameras can usually take pictures and additionally sound and video. Some can be used like webcams, some can use the PictBridge standard to connect to a printer without using a computer, and some can display pictures directly on a television set. Similarly, many camcorders can take still photographs, and store them on videotape or on flash memory cards. Most digital cameras can connect directly to a computer in order to store pictures or to be used as a webcam. Digital cameras generally include a USB or FireWire port, and a memory card slot. Some digital cameras can record movies but may be limited by storage capacity. A 1GB memory card will store approximately 1 hour's worth of video in an MP4 format. Newer digital cameras, such as the Canon PowerShot S1 IS, Canon PowerShot SD200/300 and the Pentax Optio MX/MX4 will capture continuous footage at a rate of 30 frames per second at a display resolution of 640x480 pixels (similar to a television screen). Some digital cameras can connect directly to a computer and store video on the computer's hard disk or DVD recorder.

Performance metrics

The quality of a digital image is the sum of various factors many of which are similar to film cameras. Pixel count (typically listed in megapixels,millions of pixels) is only one of the major factors, though it is the most heavily marketed. Pixel count metrics were created by the marketing organizations of digital camera manufacturers because consumers can use it to easily compare camera capabilities. It is not, however, the major factor in evaluating a digital camera. The processing system inside the camera that turns the raw data into a color-balanced and pleasing photograph is the most critical, which is why some 4+ megapixel cameras perform better than higher-end cameras in a few cases.
- Lens quality: resolution, distortion, dispersion (see Lens (optics))
- Capture medium: CMOS, CCD, Negative film, Reversal Film etc.
- Capture format: pixel count, digital file type (RAW, TIFF, JPEG), film format (135 film, 120 film, 5x4, 10x8).
- Processing: digital and / or chemical processing of 'negative' and 'print'.

Pixel counts

The number of pixels n for a given maximum resolution (w horizontal pixels by h vertical pixels) can be found using the formula: n = wh. This yields e. g. 1.92 megapixels (= 1,920,000 pixels) for an image of 1600 x 1200. The majority of digital cameras have a 4:3 aspect ratio, i.e. w/h = 4/3. The megapixel or pixel count quoted by the manufacturers is misleading because it is not truly representative of the number of full colour pixels. For cameras using a Bayer sensor it is the number of single coloured photosites (light sensitive areas) on the sensor. For the Foveon X3 sensor the number currently (Feb 2004 - Sigma SD-10) presented by Sigma is the number of photosites times three (multiplied because each photosite records three colours), however the images that result will have a number of pixels equivalent to the number of photosites - not the tripled number quoted. It is not possible to directly compare the megapixel ratings of these two sensors but in many people's opinions a 6 MP Bayer filter sensor is roughly equivalent to a 10.2 MP Foveon X3 (3.4 MP
- 3). Some hold the opinion that the Foveon is worse than this and the ratio is more like one Bayer to two Foveon. It is largely a matter of personal opinion so prints from the two sensors should be inspected by interested parties.

Possible problems

Foveon X3 sensor] Foveon X3 sensor Since the light sensitive component in a digital camera consists of discrete pixels, problems of Moiré, or interference patterns may occur when photographing fine patterns, such as textiles, geometric figures, and computer or TV screens. The example at left shows severe Moirés in a shot of a TV screen. "Highlight burn-out" is also a potential problem. Depending on the contrast of the subject, the lightest parts of the image may be so over-exposed that there is no image information, other than total white, in these highlights. Also, the reverse may occur. Shadows parts of the image may become murky to totally black, because of the inability of the camera's sensor to cope with the contrast. The image at right shows both these conditions simultaneously. Some digital cameras can show these blown highlights in the image review, allowing the photographer to reshoot the picture with a modified exposure.

Applications and considerations

With the acceptable image quality and the other advantages of digital photography (particularly the time pressures, of vital importance to daily newspapers) an increasing number of professional news photographers have begun capturing their images with digital cameras. Digital photography has also been adopted by many amateur snapshot photographers, who take advantage of the convenience of the form when sending images by email or placing them on the World Wide Web. Digital cameras have also been integrated into many cell phones, although, because of the small lens, the quality of these pictures makes them unsuitable for making even moderate size prints. Some commercial photographers, and some amateurs interested in artistic photography, have been resistant to using digital rather than film cameras because they believe that the image quality available from a digital camera of a given price is still inferior to that available from a film camera, and the quality of images taken on medium format film is near-impossible to match at any price with a digital camera. Some have expressed a concern that changing computer technology may make digital photographs inaccessible in the future while printed images have a very long lifespan. A related concern in a specialized application is the use of digital photographs in court proceedings, with the perceived difficulty of demonstrating an image's authenticity. Other commercial photographers, and many amateurs, have enthusiastically embraced digital photography because they believe that its flexibility and lower long-term costs outweigh its initial price disadvantages. Almost all of the cost of digital photography is capital cost, meaning that the cost is for the equipment needed to store and copy the images, and once purchased requires virtually no further expense outlay. Film photography requires continuous expenditure of (much higher amounts of) funds for supplies and developing. Some commercial photographers have also begun moving to digital technology because of the tremendous editing capabilities now offered on computers. The photographer is able to color-balance and manipulate the image in ways that traditional darkroom science cannot offer. With fully color-balanced systems from the camera to the monitor to the printer, the photographer can now print what is actually seen on the screen. However, digital cameras require batteries that need to be recharged frequently, and this means that a photographer needs access to electrical outlets. For this reason, photographers who work in remote areas, such as those who work for National Geographic overwhelming favor film SLR cameras. Digital photography was used in astronomy long before its use by the general public and had almost completely displaced photographic plates by the early 1980s. Not only are CCDs more sensitive to light than plates, but have much more uniform and predictable response, and the information can be downloaded onto a computer for data analysis. The CCDs used in astronomy are similar to those used by the general public, but are generally monochrome and cooled to liquid nitrogen temperatures so as to reduce the noise which is caused by heat. Many astronomical instruments have arrays of many CCDs, sometimes totalling almost a billion pixels. Nowadays amateur astronomers also commonly use digital cameras, including the use of webcams for speckle imaging or "video astronomy".

Sensor size and angle of view

Cameras with digital sensors that are smaller than the typical 35mm film size will have a smaller field or angle of view when used with a lens of the same focal length. This is because angle of view is a function of both focal length and the sensor or film size used. Image:kids_50mm_100mm.jpg If a sensor smaller than the camera's original film format is used, such as the use of APS-C-sized digital sensors in 35mm format digital SLRs, then the image's field of view is cropped by the sensor giving the impression that the focal length of the lens has changed. If the digital sensor has approximately the same resolution (effective pixels per unit area) as the 35mm film surface (24 x 36 mm), then the result is similar to taking the image from the film camera and cutting it down (cropping) to the size of the sensor. For an APS-C size sensor, this would be a reduction to approximately the center 50% of the image. The cheaper, non-SLR models of digital cameras typically use much smaller sensor sizes and the reduction would be greater. If the digital sensor has a higher or lower density of pixels per unit area than the film equivalent, then the amount of information captured will differ correspondingly. While resolution can be estimated in pixels per unit area, the comparison is complex since most types of digital sensor record only a single colour at each pixel location, and different types of film will have different effective resolutions. There are various trade-offs involved, since larger sensors are more expensive to manufacture and require larger lenses, while sensors with higher numbers of pixels per unit area are likely to suffer higher noise levels. For these reasons, it is possible to obtain cheap digital cameras with sensor sizes much smaller than 35mm film, but with high pixel counts, that can still produce high-resolution images. Such cameras are usually supplied with lenses that would be classed as extremely wide angle on a 35mm camera, and which can also be smaller size and less expensive, since there is a smaller sensor to illuminate. For example, a camera with a 1/1.8" sensor has a 5.0x field of view crop, and so a hypothetical 5-50mm zoom lens will produce images that look similar (again the differences mentioned above are important) to those produced by a 35mm film camera with a 25–250mm lens, while being much more compact than such a lens for a 35mm camera since the imaging circle is much smaller. This can be useful if extra telephoto reach is desired, as a certain lens on an APS sensor will produce an equivalent image to a significantly longer lens on a 35mm film camera shot at the same distance from the subject, the equivalent length of which depends on the camera's field of view crop. This is sometimes referred to as the focal length multiplier, but the focal length is a physical attribute of the lens and not the camera system itself. The downside to this is that wide angle photography is made somewhat more difficult, as the smaller sensor effectively and undesirably reduces the captured field of view. Some methods of compensating for this or otherwise producing much wider digital photographs involve using a fisheye lens and "defishing" the image in post processing to simulate a rectilinear wide angle lens. As of 2005, only a few high-end DSLR camera models from Canon and Kodak have sensor sizes that match a 35mm film frame. This is the ideal size for maximising the use of lenses designed for a 35mm camera, since it can reproduce the effect smaller sizes by cropping the image (assuming equal pixel density). Common values for field of view crop in DSLRs include 1.3x for some Canon sensors, 1.5x for Sony APS-C sensors used by Nikon, Pentax and Konica Minolta, 1.6 (APS-C) for most Canon sensors and Fujifilm sensors, ~1.7x for Sigma's Foveon sensors and 2x for Kodak 4/3" sensors currently used by Olympus. Crop factors for non-SLR consumer and prosumer cameras are larger, frequently 4x or more.

File types and data storage formats

Exchangeable image file format (Exif) is a set of file formats specified for use in digital cameras. This specifies the use of TIFF for the highest quality format and JPEG as a space-saving but lower quality format. Many low-end cameras can deliver only JPEG files. Another format that may be encountered is CCD-RAW, which is not standardised. A large variety of data storage device formats are used in consumer digital cameras:
- Secure Digital Card (SD)
- Compact Flash (CF-I and CF-II)
- Memory Stick
- Multi Media Card (MMC)
- SmartMedia
- xD-Picture Card (xD)
- USB keydrive Most manufacturers of digital cameras do not provide drivers and software to allow their cameras to work with Linux or other free software. Still, many cameras use the standard USB storage protocol, and are thus easily usable. Other cameras are supported by the gPhoto project.

Digital camera backs

:main article Digital camera back Most digital cameras are built to operate as a self-contained unit. This is especially so at the lower-end, for these cameras usually include zoom lens and flashes that cannot be changed. However, at the highest-end, some digital cameras are nothing but a sophisticated light-sensing unit. Experienced photographers attach these digital "camera backs" to their professional medium format SLR cameras, such as a Hasselblad.
- Area array
- CCD
- CMOS
- Linear array
- CCD (monochrome)
- 3-strip CCD with color filters Linear array cameras are also called scan backs.
- Single-shot
- Multi-shot (three-shot, usually) These camera backs are originally used only in a studio to take pictures of still objects. Most earlier digital camera backs were using linear array sensors which could take seconds or even minutes for a complete high-resolution scan. The linear array sensor acts like its counterpart in a flatbed image scanner by moving vertically to digitize the image. Many of these cameras could only capture grayscale images. To take a color picture, it requires three separate scans done with a rotating colored filter. These are called multi-shot backs. Some other camera backs are using CCD arrays similar to typical cameras. These are called single-shot backs. Since it is much easier to manufacture a high-quality linear CCD array that has only thousands of pixels than a CCD matrix that has millions of them, very high resolution linear CCD camera backs were available much earlier than their CCD matrix counterparts. For example, you could buy an, albeit expensive, camera back with over 7,000 pixel horizontal resolution in the mid-1990s. However, as of 2004, it is still difficult to buy a comparable CCD matrix camera of the same resolution. Many modern digital camera backs are using very large CCD matrices. This eliminated the need of scanning. For example, Fujifilm produces a 20 million pixel digital camera back with a 52 x 37 mm (2.04 x 1.45 inch) CCD in 2003. This CCD array is a little smaller than a frame of 120 film and much larger than a 35 mm frame (36 x 24 mm). In comparison, a consumer digital camera usually uses a much smaller 1/2.5 inch or 7.176 x 5.329 mm (~ 1/1.8 inch) CCD sensor. Further, the 1/2.5 or 1/1.8 inch diagonal measurement is the size of the entire CCD chip- the actual photo-sensitive area is much smaller. A digital camera back is a good idea to smooth the transition from film to digital. A photographer can reuse his existing SLR camera and lens without much trouble. To some medium format camera users, the convenience of a bellows has no substitute.

Comparison with film cameras

Advantages of digital: consumer cameras

The advantages of digital photography over traditional film include:
- Instant review of pictures, with no wait for the film to be developed: if there's a problem with a picture, the photographer can immediately correct the problem and take another picture.
- Only successful pictures need to be printed. This means you can take many shots of the same scene but with slightly different settings, then choose the best one. Doing this with film would be too expensive.
- Minimal ongoing costs for those wishing to capture hundreds of photographs for digital uses, such as computer storage and e-mailing, but not printing.
- If one already owns a newer computer, permanent storage on digital media is considerably cheaper than film.
- Images may be copied from one media to another without any degradation.
- Pictures do not need to be scanned before viewing them on a computer.
- Ability to print your own pictures using a computer and consumer-grade printer.
- Ability to print your own pictures using printers that can communicate directly with the camera, or its memory card, for computer-less printing.
- Digital cameras can be much smaller than film cameras of equivalent quality.
- Ability to embed meta data within the image, such as the time and date of the photograph, model of the camera, shutter speed, flash use, film speed, and other similar items, to aid in the reviewing and sorting of photographs.
- Ability to capture and store hundreds of photographs on the same media device within the digital camera; by contrast, a film camera would require regular changing of film (after say, every 24 or 27 shots).
- Many digital cameras now include an AV-out function (and cable) to allow the reviewing of photographs to an audience using a television.
- Digital image files can be backed up to CD-ROM or DVD-ROM, although, it is believed that negatives will probably last at least as long as, if not longer than CD-ROMs.

Advantages of digital: professional cameras

- Immediate image review and removal, lighting and composition can be assessed without wasting storage space.
- The ability to shoot in RAW format (images that contain tagged data directly from the sensor). However, as of this writing, there are a number of proprietary RAW formats, some of which require specific software to manipulate.
- Faster workflow: Management (colour and file), manipulation and printing tools are more versatile than conventional film processes. However, batch processing of RAW files can be time consuming, even on a fast computer. Recent digital cameras from leading manufacturers such as Nikon and Canon have promoted the adoption of digital Single-lens reflex cameras (dSLRs) by photojournalists. Images captured at 2+ megapixels are deemed to be of sufficient quality for small images in newspaper or magazine reproduction. Six to 12 megapixel images, found in modern digital SLRs, when combined with high-end lenses, can approximate the detail of film prints taken with 35 mm film based SLRs, and the latest 16 megapixel models can produce astoundingly detailed images which are believed to be better than 35mm film images and the majority of medium format cameras. [http://www.luminous-landscape.com/reviews/shootout.shtml]

Disadvantages of digital cameras

- Equivalent film cameras are much less expensive than digital cameras.
- Batteries may last longer in film cameras than in digital cameras, and some manual film cameras require no batteries at all.
- At some ISO levels film is available that shows less grain / noise than digital cameras.
- There are special types of film, such as for infrared light, that have no equivalent in digital.
- Other than high-end digital SLRs, film cameras can offer much greater flexibility in changing the depth of field for an image.
- Film is capable of much greater resolution than digital photographs. Estimated resolutions are; 35mm film - 19 megapixels, 120 film - 69 megapixels, Large format - 1135 megapixels versus 297 megapixels for [http://www.betterlight.com/superModels.asp] expensive digital backs
- A film camera does not require a computer to download images to. However, a number of stores with one hour photo labs can now make prints of digital images using the camera's memory card. In addition, newer photo printers that use PictBridge technology can make prints of digital images without a computer.
- Film and prints can be easily stored in a file cabinet. Digital images stored on a computer can be lost if a hard drive fails; CD-ROMs may be a good alternative, but no one knows if computers that can read them will be widely available 100 years from now. For most consumers in prosperous countires, such as the United States and Western Europe, the advantages of digital cameras outweigh their disadvantages. However, the professional photography community is split on the issue. Problems some professional photographers have voiced include: editing and post-processing of RAW files can take longer than 35 mm film, downloading a large number of images to a computer can take away from valuable shooting time, shooting in remote sites requires the photographer to carry a number of batteries and add to the load she must carry, all cameras break from time to time -- film cameras can often be fixed on the spot but digital cameras often can not. As time passes, it is expected that more professional photographers will switch to digital.

Equivalent features

- Image noise / grain: Film grain is equivalent to image noise. At high ISO levels (film speed) the grain/noise becomes more apparent in the final image. Although film ISO levels can be lower than digital ISO levels (25 and 50 respectively), digital settings can be changed quickly according to requirements, while film must be physically replaced. Additionally, image noise reduction techniques can be used to remove noise from digital images and film grain is fixed. From an artistic point of view, film grain and image noise may be desirable when creating a specific mood for an image. Modern digital cameras have comparable noise/grain at the same ISO as film cameras. Some digital cameras though, do exhibit a pattern in the digital noise which is not found on film.
- Speed of use: Current digital and film cameras can be switched on and take images instantly. Saving images to disk takes no longer than winding on the film (see Frames per second).
- Frames per second: The maximum number of frames per second (frame/s) achievable on digital and film cameras is 8 frame/s (Nikon D2H digital SLR, Nikon F5 35 mm film SLR). The Canon EOS-1D Mark II can achieve 8.5 frame/s which makes it the fastest SLR camera in the world. The F5 is limited to 36 continuous frames (the length of the film) while the D2H is able to take 40 images before its buffer must be cleared and the remaining space on the storage media can be used.
- Image longevity: Although digital image data does not degrade (film stock can fade), the media on which the digital images are stored can decay or become corrupt, leading to a loss of image integrity. Both formats should be stored under archival conditions for maximum longevity. Perfect copies of digital images can be made on fresh media whereas copying negatives or transparencies incurs additional noise and loss of detail.
- Colour reproduction: Colour reproduction (gamut) is dependent on the type of film / sensor used and the quality of the capture media, lens group and processing. Different films and sensors are sensitive to differing subsets of colour thus the photographer needs to have an understanding of the light conditions and the media used to ensure accurate colour reproduction. Many digital cameras offer RAW format (sensor data) which makes it possible to choose color space on development stage regardless of camera settings.

A comparison of frame aspect ratios

A typical digital camera's aspect ratio is 1.33 (4:3), the same as today's NTSC or PAL/SECAM TVs or earliest movies. However, a 35 mm picture's aspect ratio is 1.5 (3:2). Several new digital cameras will take photos in either ratio and nearly all digital SLRs take pictures in a 3:2 ratio as they usually use lenses designed for 35mm film (Olympus digital SLRs are a notable exception). Photo labs also offer the option of printing photos on 4:3 ratio paper, as well as the existing 3:2. In 2005 Panasonic launched the first consumer camera with a native aspect ratio of 16:9.

Market impact

In late 2002, 2 megapixel cameras were available in the United States for less than $100, with some 1 megapixel cameras for under $60. At the same time, many discount stores with photo labs introduced a "digital front end," allowing consumers to obtain true chemical prints (as opposed to ink-jet prints) in an hour. These prices were similar to those of prints made from film negatives. However, because digital images have a different aspect ratio than 35 mm film images, people have started to realize that 4x6 inch prints crop some of the image off the print. Some photofinishers have started offering prints with the same aspect ratio as the digital cameras record. In July 2003, digital cameras entered the single-use market with the release of the Ritz Dakota Digital, a 1.2 megapixel (1280 x 960) CMOS-based digital camera costing only $11 (USD). Following the familiar single-use concept long in use with film cameras, the Dakota Digital was intended to be used by a consumer one time only. When the pre-programmed 25 picture limit is reached, the camera is returned to the store, and the consumer receives back prints and a CD-ROM with their photos. The camera is then refurbished and resold. Since the introduction of the Dakota Digital, a number of similar single-use digital cameras have appeared. Most of the various single-use digital cameras are nearly identical to the original Dakota Digital regarding specifications and functionality, although a few include superior specifications and more advanced functions (such as higher image resolutions and LCD screens). Most, if not all, of these single-use digital cameras cost less than $20 (USD), not including processing fees. The price of 35mm compact cameras have dropped with manufacturers further outsourcing to countries such as China. Kodak announced in January 2004 that they would no longer sell Kodak-branded film cameras in the developed world [http://www.theregister.co.uk/2004/01/20/kodak_to_drop_35mm_cameras/]. Nikon has pulled out of the 35mm compact camera market but not the 35mm SLR market, which has been less affected since high quality digital SLR cameras are still considerably more expensive than their 35mm counterparts. Pentax have reduced production of film cameras but not halted it. [http://www.photographyblog.com/index.php/weblog/comments/pentax_to_reduce_film_compact_and_slr_production/]. The technology has improved so rapidly that one of Kodak's film cameras was discontinued before it was awarded a "camera of the year" award later in the year. Since 2002, digital cameras have outsold film cameras. Howver,the use of 35mm cameras is greater in developing countries. [http://cio.co.nz/cio.nsf/0/7FAAE94969D13C78CC256F18007D9C8F?OpenDocument] It remains to be seen if 35 mm film will remain the medium of choice as countries like China advance rapidly. The decline in film camera sales has also led to a decline in purchases of film for such cameras. In November 2004, a German division of Agfa-Gevaert, AgfaPhoto, split off. Within six months it filed for bankruptcy . In addition, by 2005, Kodak employed less than a third of the employess that it had twenty years earlier. It is not known if these job losses in the film industry have been offset in the digital image industry.

Social impact

Throughout the history of photography, technological advances in optics, camera production, developing, and imaging have had an effect on the way people view images. Prior to the 1970s, most people in the United States used slide or chrome film and viewed the images with a slide projector. After that, people began to make prints from color negatives. The simultaneous increased use of the Internet and email, relatively cheap computers and digital cameras led to a tremendous increase in the number of photographic images in digital formats. In the early part of the 21st century, the dominant method of viewing still images has been on computers and, to a lesser extent, on cellular phones (although people still make and look at prints). These factors have led to a decrease in film and film camera sales and film processing, and has had a dramatic effect on companies such as Fuji, Kodak, and Agfa. In addition, many stores that used to offer photofinishing services or sell film no longer do, and those that do have seen a tremendous decline. Photographic images have always been prone to fading and loss of image quality due to sun exposure or improper storage of film negatives, slides, and prints. Since most people who take digital pictures store them on their computer hard drives, loss of images because a hard drive fails or because a computer is otherwise broken, lost, or stolen has become a new problem people need to consider when archiving their pictures. It is likely that film will never again be purchased and used on the scale it was for most of the 20th century. However, it probably will not disappear altogether. At its advent at the start of the 20th century, many believed photography would supplant the painting of portraits and landscapes. This was largely true, but oil and acrylic paint have not vanished entirely. In the same way it's likely photographic film and equipment will continue to be an option for enthusiasts.

External links

- [http://news.bbc.co.uk/1/hi/magazine/3399529.stm R.I.P. 35mm Camera, BBC News Online]
- [http://news.bbc.co.uk/2/hi/business/3394183.stm BBC News (01/13/2004): Kodak embraces digital revolution]
- [http://www.cambridgeincolour.com/tutorials.htm Digital photography tutorials]
- [http://www.nationalgeographic.com/adventure/0306/q_n_a.html National Geographic Adventure Mag.: Q & A with Photographer Jim Brandenburg]
- [http://www.nicholsonprints.com/Articles/digital.htm Digital vs. film: One photographer's experience]
- [http://www.geller-grimm.de/genera18.htm Close-up insect photography with the Nikon Coolpix] Category:Digital photography

Photography

Photography is the process of making pictures by means of the action of light. It involves recording light patterns, as reflected from objects, onto a sensitive medium through a timed exposure. The process is done through mechanical, chemical or digital devices commonly known as cameras. The word comes from the Greek words φως phos ("light"), and γραφις graphis ("stylus", "paintbrush") or γραφη graphê, together meaning "drawing with light" or "representation by means of lines" or "drawing."

Photographic image forming devices

Most commonly a camera or camera obscura is the image forming device and photographic film or a digital storage card is the recording medium, although other methods are available. For instance, the photocopy or xerography machine forms permanent images but uses the transfer of static electrical charges rather than photographic film, hence the term electrophotography. The rayographs published by Man Ray in 1922 are images produced by the shadows of objects cast on the photographic paper, without the use of a camera. And one can place objects directly on the glass of a scanner to produce pictures electronically. Photographers control the camera to expose the light recording material (usually film or a charge-coupled device) to light. After processing, this produces an image whose contents are acceptably sharp, bright and composed to achieve the objective of taking the photograph. The controls include:
- Focus
- Aperture of the lens
- Duration of exposure (or shutter speed)
- Focal length of the lens (telephoto, macro, wide angle, or zoom)
- Sensitivity of the medium to light intensity and color The controls are usually inter-related, for example brightness is aperture multiplied by shutter speed, and varying the focal length of the lens will allow greater control over the depth of field. Depth of field is the area of the image that is in focus. The larger the depth of field, the larger the area of the image that is in focus. The smaller the depth of field, the smaller the area that is in focus. A higher aperture setting, like f16 or f22, gives the photographer a smaller depth of field. A lower aperture setting, like f1.4 or f2.8, gives a larger depth of field.

Uses of photography

Photography can be classified under imaging technology and has gained the interest of scientists and artists from its inception. Scientists have used its capacity to make accurate recordings, such as Eadweard Muybridge in his study of human and animal locomotion (1887). Artists have been equally interested by this aspect but have also tried to explore other avenues than the photo-mechanical representation of reality, such as the pictorialist movement. Military, police and security forces use photography for surveillance, recognition and data storage.

History of photography

pictorialist pictorialist

Invention

Chemical photography

Projecting images onto surfaces has been done for centuries. The camera obscura and the camera lucida were used by artists to trace scenes as early as the 16th century. These early cameras did not fix an image in time; they only projected what was before an opening in the wall of a darkened room onto a surface. In effect, the entire room was turned into a large pinhole camera. Indeed, the phrase camera obscura literally means "darkened room," and it is after these darkened rooms that all modern cameras have been named. The first photograph is considered to be an image produced in 1826 by the French inventor Nicéphore Niépce on a polished pewter plate covered with a petroleum derivative called bitumen of Judea. It was produced with a camera, and required an eight hour exposure in bright sunshine. However, this process turned out to be a dead end and Niépce began experimenting with silver compounds based on a Johann Heinrich Schultz discovery in 1724 that a silver and chalk mixture darkens when exposed to light. Niépce, in Chalon-sur-Saône, and the artist Jacques Daguerre, in Paris, refined the existing silver process in a partnership. In 1833 Niépce died unexpectedly of a stroke, leaving his notes to Daguerre. While he had no scientific background, Daguerre made two pivotal contributions to the process. He discovered that by exposing the silver firstly to iodine vapour, before exposure to light, and then to mercury fumes after the photograph was taken, a latent image could be formed and made visible. By then bathing the plate in a salt bath the image could be fixed. In 1839 Daguerre announced that he had invented a process using silver on a copper plate called the Daguerreotype. A similar process is still used today for Polaroids®. The French government bought the patent and immediately made it public domain. Across the English Channel, William Fox Talbot had earlier discovered another means to fix a silver process image but had kept it secret. After reading about Daguerre's invention, Talbot refined his process, so that it might be fast enough to take photographs of people as Daguerre had done, and by 1840 he had invented the calotype process. He coated paper sheets with silver chloride to create an intermediate negative image. Unlike a daguerreotype, a calotype negative could be used to reproduce positive prints, like most chemical films do today. Talbot patented this process, which greatly limited its adoption. He spent the rest of his life in lawsuits defending the patent until he gave up on photography all together. But later this process was refined by George Eastman and is today the basic technology used by chemical film cameras. Hippolyte Bayard also developed a method of photography, but delayed announcing it and so was not recognized as its inventor. Hippolyte Bayard

Reference

- Coe, Brian. The Birth of Photography. Ash & Grant, 1976.

Social history

Popularization

The Daguerreotype proved popular as it responded to the demand for portraiture emerging from the middle classes during the Industrial Revolution. This demand, that could not be met in volume and in cost by oil painting, may well have been the push for the development of photography. But still daguerreotypes, while beautiful, were fragile and difficult to copy. A single photograph taken in a portrait studio could cost $1000 in 2005 dollars. Photographers also encouraged chemists to refine the process of making many copies cheaply, which eventually lead them back to Talbot's process. Ultimately, the modern photographic process came about from a series of refinements and improvements in the first 20 years. In 1884 George Eastman, of Rochester, New York, developed dry gel on paper, or film, to replace the photographic plate, so that a photographer no longer needed to carry boxes of plates and toxic chemicals around. In July of 1888 Eastman's Kodak camera went on the market with the slogan "You press the button, we do the rest". Now anyone could take a photograph and leave the dangerous portions of the process to others. Photography became available for the mass-market in 1901 with the introduction of Kodak Brownie. Very little has changed in chemical photography since then, though color film has become the standard, as well as automatic focus and automatic exposure. Digital recording of images is becoming increasingly prevalent, as digital cameras allow instant previews on LCD screens among other benefits, and the resolution of top of the range models has exceeded high quality 35mm film while lower resolution models have become affordable. For the enthusiast photographer processing black and white film, little has changed since the introduction of the 35mm film Leica camera in 1925.

Economic history

In the nineteenth century, photography developed rapidly as a commercial service. In the U.S. in 1890, the number of professional photographers was about the same as the number of accountants, artists, and dentists, respectively, and about ten times greater than the number of authors. End-user supplies of photographic equipment accounted for only about 20% of industry revenue. Several trends characterize the photographic industry from the end of the nineteenth century to the end of the twentieth century. The ratio of revenue from end-user photographic supplies to revenue from professional services rose by an order of magnitude. The prevalence of personal cameras and the ratio of end-user photographs rose closely in tandem with the prevalence of telephone and the telephone conversation minutes. However, the ratio of photographic industry revenue to telephone industry revenue dropped sharply.[http://www.galbithink.org/sense-s6.htm#wpp1] Given the development of new digital technologies for creating and sharing images, and of new communications devices, e.g. camera phones, understanding the economics of image use are becoming increasingly important for understanding the evolution of the communications industry as a whole. Resources Jenkins, Reese V. Images & Enterprise: Technology and the American Photographic Industry 1839-1925. Baltimore, The Johns Hopkins University Press, 1975. The book provides a fine overview of the economics of photography and is especially strong on the growth and development of the Eastman Kodak Company.

Color photography

Main article: color photography Color photography was explored throughout the 1800s. Initial experiments in color could not fix the photograph and prevent the color from fading. The first permanent color photo was taken in 1861 by the physicist James Clerk Maxwell. One of the early methods of taking color photos was to use three cameras. Each camera would have a color filter in front of the lens. This technique provides the photographer with the three basic channels required to recreate a color image in a darkroom or processing plant. Practical application of the technique was held back by the very limited colour response of early film; however, in the early 1900s, following the work of photo-chemists such as H. W. Vogel, emulsions with adequate sensitivity to green and red light at last became available. The first color film, Autochrome, thus did not reach the market until 1907; it was based on a 'screen-plate' filter made of dyed dots of potato starch. The first modern ('integrated tri-pack') color film, Kodachrome, was introduced in 1935 based on three colored emulsions. Most modern color films, except Kodachrome, are based on technology developed for Agfacolor (as 'Agfacolor Neue') in 1936. Instant color film was introduced by Polaroid in 1963. Color photography may form images as a positive transparency, intended for use in a slide projector or as color negatives, intended for use in creating positive color enlargements on specially coated paper. The latter is now the most common form of film (non-digital) color photography, owing to the introduction of automated photoprinting equipment.

Digital photography

Main article: digital photography digital photography Traditional photography was a considerable burden for photographers working at remote locations (such as press correspondents) without access to processing facilities. With increased competition from television, there was pressure to deliver their images to newspapers with greater speed. Photo-journalists at remote locations would carry a miniature photo lab with them, and some means of transmitting their images down the telephone line. In 1981, Sony unveiled the first consumer camera to use a CCD for imaging, and which required no film -- the Sony Mavica. While the Mavica did save images to disk, the images themselves were displayed on television, and therefore the camera could not be considered fully digital. In 1990, Kodak unveiled the DCS 100, the first commercially available digital camera. Its cost precluded any use other than photojournalism and professional applications, but commercial digital photography was born. Digital photography uses an electronic sensor such as a charge-coupled device to record the image as a piece of electronic data rather than as chemical changes on film. Some other devices, such as cell phones, now include digital photography features. In 10 years, digital cameras have become widespread consumer products. Digital cameras now outsell film cameras, and many include features not found in film cameras such as the ability to shoot video and record audio. Kodak announced in January 2004 that it would no longer produce reloadable 35-millimeter cameras after the end of that year. This was interpreted as a sign of the end of film photography. However, Kodak was at that time a minor actor on the reloadable film cameras market. The price of 35mm and APS compact cameras have dropped, probably due to direct competition from digital and the resulting growth of the offer of second-hand film cameras. However, "wet" photography may endure, as dedicated amateurs and skilled artists often prefer the use of traditional and familiar materials and techniques.

Commercial photography

The commercial photographic world is traditionally broken down to:
- Advertising photography: photographs done to illustrate a service or product. These images are generally done with an Advertising Agency, Design Firm or with an in-house Corporate design team.
- Editorial photography: photographs done to illustrate a story or idea within the context of a magazine. These are usually assigned by the magazine.
- Photojournalism: this can be considered a subset of Editorial. Photographs done in this context are accepted as a truthful documentation of a news story.
- Portrait and wedding photography: photographs done and sold directly to the end user of the images.
- Fine art photography: photographs created to fulfill a vision, and reproduced to be sold directly to the end user. The market for photographic services demonstrates the aphorism "one picture is worth a thousand words," which has an interesting basis in the history of photography. Magazines and newspapers, companies putting up Web sites, advertising agencies and other groups pay for photography. Many people take photographs for self-fulfillment or for commercial purposes. Organizations with a budget and a need for photography have several options: they can assign a member of the organization, hire someone, run a public competition, or obtain rights to stock photographs.

Terminology

Traditionally, the product of photography has been called a photograph. The term photo is a convenient abbreviation. Many people also call them pictures. In digital photography, the term image has begun to replace photograph. This term is neither more nor less correct than photograph, either in film or digital photography. (The term image is traditional in geometric optics.) Although not viewed by all photographers as true photography, digital photography in fact meets all requirements to be called such. Even though there are no chemical processes, a digital camera captures a frame of whatever it happens to be pointed at, which can be viewed later.

Photography as an art form

stock photographs settings can achieve unusual results]] During the twentieth century, both fine art photography and documentary photography became accepted by the English-speaking art world and the gallery system. In the USA, a small handful of curators spent their lives struggling to put it there, with Alfred Stieglitz, Edward Steichen and John Szarkowski, and Hugh Edwards the most prominent among them. Yet the aesthetics of photography is a matter that continues to be discussed regularly, especially in artistic circles. Is photography an art - or is it just the mechanical reproduction of an image? If photography is authentically art, what makes a photograph beautiful? Is there a kinship between the beauty of an Atget and a Rembrandt? The controversy began with the earliest images "written with light": [http://www.nicephore-niepce.com/pagus/pagus-bio.html Niépce], [http://www.rleggat.com/photohistory/history/daguerr.htm Daguerre], and others among the very earliest photographers were met with wonder, but some questioned if it was really art. Clive Bell in his classic essay "Art" states that only one thing can distinguish art from what is not art: "significant form." Bell wrote: "There must be some one quality without which a work of art cannot exist; possessing which, in the least degree, no work is altogether worthless. What is this quality? What quality is shared by all objects that provoke our aesthetic emotions? What quality is common to Sta. Sophia and the windows at Chartres, Mexican sculpture, a Persian bowl, Chinese carpets, Giotto's frescoes at Padua, and the masterpieces of Poussin, Piero della Francesca, and Cezanne? Only one answer seems possible - significant form. In each, lines and colors combined in a particular way, certain forms and relations of forms, stir our aesthetic emotions." [http://www.csulb.edu/~jvancamp/361r13.html Text of Bell's essay].

Aesthetic realism and photography

Clive Bell Others have since examined if this criterion be applied to photography. This question has been examined by the aesthetic realism understanding of beauty. Some of the most important writing on this subject is to be found on the web sites of Len Bernstein, [http://www.dienes-and-dienes.com/Atget.html Louis Dienes], [http://www.dienes-and-dienes.com/Cartier-Bresson.html Amy Dienes], and [http://www.mindspring.com/~davidmbernstein/Dorothea_Lange.html David M. Bernstein]: photographers and critics. Len Bernstein has described the [http://www.lenbernstein.com/ Aesthetic Realism understanding of photography as an art form] in essays which have been published for example in [http://www.apogeephoto.com/apr2001/bernstein4_2001.shtml Apogee Photo Magazine] and in [http://lenbernstein.com/Pages/RiisArticle.html Photographica World: The Journal of the Photographic Collectors Club of Great Britain]. On his web site he introduces the subject as follows: "When I began to photograph more than 25 years ago, I felt I found a way of expressing myself that met something so deep inside me that I wanted to do it for the rest of my life. Walking with my camera, the city streets seemed transformed - friendlier, more interesting - and I spent hours searching for dramatic situations, trying to capture the right moment. Looking through the viewfinder, what I saw had new value for me, boredom and loneliness seemed to vanish, and I wished I could feel that way all the time. And hoping to learn what made a photograph successful, I avidly studied the history and technique of photography. "My hopes were met when I first heard this magnificent statement by Eli Siegel, the American critic and founder of the philosophy Aesthetic Realism: [http://www.terraingallery.org/IsBeauty.html 'All beauty is a making one of opposites, and the making one of opposites is what we are going after in ourselves.'] This is the criterion for beauty that centuries of artists, philosophers, people in all walks of life, have searched for; the explanation of what makes a photograph good and how our personal questions are the questions of art - dignified and cultural! I've had the thrill of testing it in thousands of instances, from the first known photograph taken by Nicéphore Niépce in 1826-27 to the most modern work of today." [http://lenbernstein.com/PagesLargeImages/peopleparkbench.html For an online exhibition of Bernstein's photographs click here.] Likewise, important articles (referred to above) on photography as an art form, written from the Aesthetic Realism point of view, will be found on the David M. Bernstein web site [http://www.mindspring.com/~davidmbernstein/Dorothea_Lange.html "What Does a Person Deserve? The Answer Found in a Great Photograph"] and the "Dienes & Dienes" web site. See, for example Amy Dienes' [http://www.dienes-and-dienes.com/Cartier-Bresson.html "The Self Alone & The Self Going Out; or, Cartier-Bresson's Photo of a Leaping Man"]; Louis Dienes' [http://www.dienes-and-dienes.com/Atget.html "On a Photograph by Eugene Atget"] and his illustrated poem "Black and White," originally composed for his own exhibition of photographs, which begins: [http://www.dienes-and-dienes.com/Photographs-and-A-Poem-1st.html "The day black and white got a break..."] An often neglected form of art in photography is that of portrait photography. A portrait is the basic rendering of someone’s likeness. A good portrait photographer not only wants to capture the true likeness, but also the personality of the individual. The photographer needs to be proficient not only in the workings and setting of the camera, but also needs to understand form and lighting. Great lighting and positioning can make someone appear at their best form if used correctly. Lighting and camera placement can also aid in correcting defects such as shortening a nose, making someone appear slimmer, etc. In this form of art, portrait photography takes on many roles, and can help create various moods that the individual is seeking.

Reference

Tom Ang, Dictionary of Photography and Digital Imaging, The Essential Reference for the Modern Photographer (Argentum 2001)

Additional reading

- Freeman Patterson, Photography and The Art of Seeing, 1989, Key Porter Books, ISBN 1550130994.
- The Oxford Companion to the Photograph, ed. by Robin Lenman, Oxford University Press 2005

External links

- [http://www.digitalkb.com/digital_photography/knowledge_base/exposure/ Understanding Exposure and Digital Cameras (Image Sensors)]
- [http://www.dofmaster.com Depth of Field Calculators]
- [http://www.dpreview.com dpreview.com] digital camera reviews
- [http://www.photopermit.org PhotoPermit.Org] discussion on copyright law for photographers
- [http://www.luminous-landscape.com/ The Luminous Landscape] - photography techniques and camera reviews
- [http://photoinf.com/ Photography Composition Articles]
- [http://www.mccord-museum.qc.ca/en/keys/webtours/VQ_P3_2_EN.html Instant Memories] — the origins of amateur photography
- [http://www.mccord-museum.qc.ca/en/keys/webtours/VQ_P2_7_EN.html In the Eye of the Camera] — The limits of photography in 19th century
- [http://www.floridamemory.com/OnlineClassroom/photographic-processes/index.cfm Daguerreotype to Digital: A Brief History of the Photographic Process] From the State Library & Archives of Florida. Category:Arts Category:News Category:Photography ja:写真 th:การถ่ายภาพ

Photographic film

Photographic film is a sheet of plastic (polyester, celluloid (nitrocellulose) or cellulose acetate) coated with an emulsion containing light-sensitive silver halide salts (bonded by gelatin) with variable crystal sizes that determine the sensitivity and resolution of the film. When the emulsion is subjected to controlled exposure to light (or other forms of electromagnetic radiation such as X-rays), it forms a latent (invisible) image. Chemical processes can then be applied to the film to create a visible image, in a process called film developing. In black-and-white photographic film there is usually one layer of silver salts. When the exposed grains are developed, the silver salts are converted to metallic silver, which block light and appear as the black part of the film negative. Color film uses at least three layers. Dyes added to the silver salts make the crystals sensitive to different colors. Typically the blue-sensitive layer is on top, followed by the green and red layers. During development, the silver salts are converted to metallic silver, as with black and white film. The by-products of this reaction form colored dyes. The silver is converted back to silver salts in the bleach step of development. It is removed from the film in the fix step. Some films, like Kodacolor II, have as many as 12 emulsion layers, with upwards of 20 different chemicals in each layer. Because photographic film was ubiquitous in the production of motion pictures, or movies, these are also known as films.

Film basics

There are two primary types of photographic film:
- Print film, when developed, turns into a negative with the colors (or black and white values, in black and white film) inverted. This type of film must be "printed" — either projected through a lens or placed in contact — to photographic paper in order to be viewed as intended. Print films are available in both black & white and color.
- Color reversal film after development is called a transparency and can be viewed directly using a loupe or projector. Reversal film mounted with plastic or cardboard for projection is often called a slide. It is also often marketed as "slide" film. This type of film is often used to produce digital scans or color separations for mass-market printing. Photographic prints can be produced from reversal film, but the process is expensive and not as simple as that for print film. Black and white reversal film exists, but is uncommon — one of the reasons reversal films are popular among professional photographers is the fact that they are generally superior to print films with regards to color reproduction. (Conventional black and white negative stock can be reversal- processed, to give 'black & white slides', and kits are available to enable this to be done by home-processors - however, the gamma required for an effective slide is high, and more easily achieved with a slower film like Pan-F). In order to produce a usable image, the film needs to be exposed properly. The range of tones that a given film can accurately record is called its exposure latitude. Color print film generally has better exposure latitude than other types of film. Additionally, because color print film must be printed to be viewed, some after-the-fact correction of the exposure can be made during the printing process. The concentration of dyes or silver salts remaining on the film after development is referred to as density. A dark image on the negative is of higher "density" than a more transparent image. If part of the image exceeds the maximum density possible for a print film, then it is overexposed and will appear as featureless white on the print. Likewise, if part of an image is beneath the minimum density possible on a film, the area will appear as featureless black. Some photographers use their knowledge of these limits to determine the optimum exposure for a photograph; for one example, see the Zone system. Most automatic cameras instead try to achieve a particular average density. Film speed describes a film's overall sensitivity to light. The international standard for rating film speed is the ISO scale (also known as ASA, since it it was initially developed by the American Standards Association). Common film speeds include ISO 25, ISO 50, ISO 64, ISO 100, ISO 160, IS0 200, ISO 400, ISO 800, ISO 1600, and ISO 3200. Consumer print films are usually in the ISO 100 to ISO 800 range. Some films, like Kodak's Technical Pan, are not ISO rated and therefore careful examination of the film's properties must be made by the photographer before exposure and development. ISO 25 film is very "slow", so it requires much more exposure to produce a usable image than ISO 800 film. Films of ISO 800 and greater (referred to as "fast" films) are thus better suited to low-light situations and action shots. The benefit of slower films is that it usually has finer grain and better colour rendition than fast film. Professional photographers usually seek these qualities, and therefore require a tripod to stabilize the camera for a longer exposure. Grain size refers to the size of the silver crystals in the emulsion. The smaller the crystals, the finer the detail in the photo. A film with a particular ISO rating can be pushed to behave like a film with a higher ISO — that is, exposed for a shorter period of time than would normally be used. In order to do this, the film must be developed for a longer amount of time than usual. This procedure is usually only performed by the photographer who does their own development, or by professional-level photofinishers. More rarely, a film can be pulled to behave like a "slower" film.

History of film

Pioneering work on the light sensivity of films was done by Hurter & Driffield from 1876 onwards; this work enabled the first quantitative measure of film speed to be devised. The first flexible photographic film was made by Eastman Kodak in 1885. This "film" was coated on paper. The first transparent plastic film was produced in 1889. Before this, glass photographic plates were used, which were far more expensive and cumbersome, albeit also of better quality. Early photography in the form of daguerreotypes did not use film at all.

Special films

Instant photography, as popularised by Polaroid, uses a special type of camera and film that automates and integrates development, without the need of further equipment or chemicals. This process is carried out immediately after exposure, as opposed to regular film, which is developed afterwards and requires additional chemicals. See instant film. Specialty films exist for recording non-visible portions of the electromagnetic spectrum. These films are usually designed to record either ultraviolet or infrared light. These films can require special equipment; for example, most photographic lenses are made of glass and will therefore filter out most ultraviolet light. Instead, expensive lenses made of quartz must be used. Film sensitized to X-ray radiation is commonly used for medical imaging, and personal monitoring.

Common sizes of film

See also Film format.
- 135 (popularly known as "35mm")
- APS (Advanced Photo System)
- 110
- 127
- 120/220 (for use in medium format photography)
- Sheet film (for use in large format photography)
- Motion picture films: 8mm, 16mm, 35mm and 70mm

Companies that manufacture photographic film

- Agfa-Gevaert
- Efke
- Foma
- Forte
- Ferrania
- Fujifilm
- Ilford
- Imation (Spin-off company of 3M has since sold off film production to Kodak.)
- Kodak
- Konica
- Lucky
- Maco
- Orwo
- Perutz (film)
- Polaroid
- ProClick
- Solaris (film)
- Svema
- Tasma
- Tura (film) Film manufacturers commonly make film that is branded by other companies. Modern films have bar codes on the edge of the film which can be read by a bar code reader. This is because film is sometimes processed differently according to specifications of the film, determined by its manufacturer; the bar code is entered into the computer printer before the film is printed. To establish the OEM, read the bar code printed on the cassette. Divide the long number by 16 and record the number before the decimal, then multiply the number after the decimal by 16, this could give you a result such as 18 and 2. The first number is known as the PRODUCT (film manufacturer) and the second number as the MULTIPLIER (speed of the film ISO). In the previous example, 18 identifies 3M as the manufacturer and 2 means it is 200 ISO:
- 3M = 18
- Agfa = 17 or 49
- Kodak = 80, 81, 82 or 88

Sensor

A sensor is a physical device or biological organ that detects, or senses, a signal or physical condition and chemical compounds.

Overview

Most sensors are electrical or electronic, although other types exist. A sensor is a type of transducer. Sensors are either direct indicating (e.g. a mercury thermometer or electrical meter) or are paired with an indicator (perhaps indirectly through an analog to digital converter, a computer and a display) so that the value sensed becomes human readable. Aside from other applications, sensors are heavily used in medicine, industry and robotics. Technical progress allows more and more sensors to be manufactured with MEMS technology. In most cases this offers the potential to reach a much higher sensitivity. See also MEMS sensor generations.

Classification of types

Since a signal involves an exchange of energy, sensors can be classified according to the type of energy transfer that they detect.

Thermal energy

- temperature sensors: thermometers, thermocouples, temperature sensitive resistors (thermistors), bi-metal thermometers and thermostats
- heat sensors: bolometer, calorimeter

Electromagnetic sensors

- electrical resistance sensors: ohmmeter, multimeter
- electrical current sensors: galvanometer, ammeter
- electrical voltage sensors: leaf electroscope, voltmeter
- electrical power sensors: watt-hour meters
- magnetism sensors: magnetic compass, fluxgate compass, magnetometer, Hall effect device

Mechanical sensors

- pressure sensors: barometer, barograph, pressure gauge, air speed indicator, rate of climb indicator, variometer
- gas and liquid flow sensors: flow sensor, anemometer, flow meter, gas meter, water meter, mass flow sensor
- mechanical sensors: position sensor, selsyn, switch, strain gauge

Chemical sensors

Chemical sensors detect the presence of specific chemicals or classes of chemicals. Examples include oxygen sensors, also known as lambda sensors, ion-selective electrodes, pH glass electrodes, and redox electrodes.

Optical and radiation sensors

- electromagnetic time-of-flight. Generate an electromagnetic impulse, broadcast it, then measure the time a reflected pulse takes to return. Commonly known as - RADAR (Radio Detection And Ranging) are now accompanied by the analogous LIDAR (Light Detection And Ranging. See following line), all being electromagnetic waves. Acoustic sensors are a special case in that a pressure transducer is used to generate a compression wave in a fluid medium (air or water)
- light time-of-flight. Used in modern surveying equipment, a short pulse of light is emitted and returned by a retroreflector. The return time of the pulse is proportional to the distance and is related to atmospheric density in a predictable way.

Ionising radiation

- radiation sensors: Geiger counter, dosimeter, Scintillation_counter
- subatomic particle sensors: scintillometer, cloud chamber, bubble chamber

Non ionising radiation

- light sensors: photocells, photodiodes, phototransistors, photo-electric tubes, CCDs, Nichols radiometer, Image sensor
- proximity sensor- A type of distance sensor but less sophisticated. Only detects a specific proximity. May be optical - combination of a photocell and LED or laser. Applications in cell phones, paper detector in photocopiers, auto power standby/shutdown mode in notebooks and other devices. May employ a magnet and a Hall effect device.
- scanning laser- A narrow beam of laser light is scaned over the scene by a mirror. A photocell sensor located at an offset responds when the beam is reflected from an object to the sensor, whence the distance is calculated by triangulation.
- focus. A large aperture lens may be focused by a servo system. The distance to an in-focus scene element may be determined by the lens setting.
- binocular. Two images gathered on a known baseline are brought into coincidence by a system of mirrors and prisms. The adjustment is used to determine distance. Used in some cameras (called range-finder cameras) and on a larger scale in early battleship range-finder
- coherent laser- interference between transmitted and reflective lightwaves are counted and the distance is calculated. Capable of extremely high precision.

Acoustic sensors

Acoustic

- sound sensors: microphones, hydrophones, seismometers. acoustic: uses ultrasound time-of-flight echo return. Used in mid 20th century polaroid cameras and applied also to robotics. Even older systems like Fathometers (and fish finders) and other 'Tactical Active' Sonar Sound Navigation And Ranging) systems in naval applications which mostly use audible sound frequencies.

Other types of sensor

- motion sensors: radar gun, speedometer, tachometer, odometer, turn coordinator
- orientation sensors: gyroscope, artificial horizon, ring laser gyroscope
- distance sensor (noncontacting) Several technologies can be applied to sense distance: magnetostriction

Non Initialized systems

- Gray code strip or wheel- a number of photodetectors can sense a pattern, creating a binary number. The gray code is a mutated pattern that ensures that only one bit of information changes with each measured step, thus avoiding ambiguities.

Initialized systems

These require starting from a known distance and accumulate incremental changes in measurements.
- Quadrature wheel- An disk-shaped optical mask is driven by a gear train. Two photocells detecting light passing through the mask can determine a partial revolution of the mask and the direction of that rotation.
- whisker sensor- A type of touch sensor and proximity sensor.

Classification of measurement errors

A good sensor applies to the following rules:
- the sensor should be sensitive to the measured property
- the sensor should be insensitive to any other property
- the sensor should not influence the measured property In the ideal situation, the output signal of a sensor is exactly proportional to the value of the measured property. The gain is then defined as the ratio between output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the gain is a constant with the unit [V/K]. If the sensor is not ideal, several types of deviations can be observed:
- The gain may in practice differ from the value specified. This is called a gain error.
- Since the range of the output signal is always limited, the output signal will eventually clip when the measured property exceeds the limits. The full scale range defines the outmost values of the measured property where the sensor errors are within the specified range.
- If the output signal is not zero when the measured property is zero, the sensor has an offset or bias. This is defined as the output of the sensor at zero input.
- If the gain is not constant, this is called nonlinearity. Usually this is defined by the amount the output differs from ideal behaviour over the full range of the sensor, often noted as a percentage of the full range.
- If the deviation is caused by a rapid change of the measured property over time, there is a dynamic error. Often, this behaviour is described with a bode plot showing gain error and phase shift as function of the frequency of a periodic input signal.
- If the output signal slowly changes independent of the measured property, this is defined as drift.
- Long term drift usually indicates a slow degradation of sensor properties over a long period of time.
- Noise is a random deviation of the signal that varies in time.
- Hysteresis is an error caused by the fact that the sensor not instantly follows the change of the property being measured, and therefore involves the history of the measured property.
- If the sensor has a digital output, the signal is discrete and is essentially an approximation of the measured property. The approximation error is also called digitization error.
- If the signal is monitored digitally, limitation of the sampling frequency also causes a dynamic error.
- The sensor may to some extent be sensitive for other properties than the property being measured. For example, most sensors are influenced by the temperature of their environment. All these deviations can be classified as systematic errors or random errors. Systematic errors can sometimes be compensated for by means of some kind of calibration strategy. Noise is a random error that can be reduced by signal processing, such as filtering, usually at the expense of the dynamic behaviour of the sensor.

Biological sensors

All living organisms contain biological sensors with functions similar to those of the mechanical devices described. Most of these are specialized cells that are sensitive to:
- light, motion, temperature, magnetic fields, gravity, humidity, vibration, pressure, electrical fields, sound, and other physical aspects of the external environment;
- physical aspects of the internal environment, such as stretch, motion of the organism, and position of appendages (proprioception);
- an enormous array of environmental molecules, including toxins, nutrients, and pheromones;
- many aspects of the internal metabolic milieu, such as glucose level, oxygen level, or osmolality;
- an equally varied range of internal signal molecules, such as hormones, neurotransmitters, and cytokines;
- and even the differences between proteins of the organism itself and of the environment or alien creatures. The human senses are examples of specialized neuronal sensors. See Sense.

Links

- [http://www.societyofrobots.com/sensors_interpret.shtml Tutorial on interpreting and analyzing recorded sensor data]
- [http://sensorwiki.org SensorWiki] - Sensor information tailored for music technologists.
- [http://www.its.bldrdoc.gov/fs-1037/dir-032/_4770.htm Federal Standard 1037C, August 7, 1996: transducer]
- [http://www.atis.org/tg2k/_sensor.html American National Standard for Telecommunications - Telecom Glossary 2000: sensor]
- [http://www.sensedu.com/ SensEdu; how sensors work]
- Overview of Sensors and Needs for Environmental Monitoring Clifford K. Ho, Alex Robinson, David R. Miller and Mary J. Davis Sensors 2005, 5, 4-37 [http://www.mdpi.net/sensors/papers/s5010004.pdf] (open access) article Category:Transducers ja:センサ

Digital audio

Digital audio describes sound recording and reproduction systems which work by using a digital representation of the audio waveform.

Technology overview

Sampling

To convert a signal from continuous time to discrete time, the value of the signal is measured at certain intervals in time. This process is known as sampling. One can think of sampling as taking "snapshots" of a certain signal as it moves continuously in time. The rate at which the values of the signal level is taken is known as the sampling rate. Modern digital audio is based on two fundamental theorems on sampling: the Nyquist Theorem and frequency analysis based on Fourier transforms. The Nyquist Theorem states it is possible to recreate perfect bandwidth-limited signals by sampling at equal to or more than twice the highest frequency component. Fourier Transforms allow signals in time domain to be broken down into an integral of sinusoidal functions multiplied by its amplitude. Since the normal human range of hearing corresponds to no more than 20 KHz, the sampling rate will have to be higher than 40 kHz to fully represent the range of human audible frequencies. According to the Nyquist Theorem it is not necessary to sample at a higher rate for accuracy, as a human audible waveform could be as perfectly recreated at either 40 kHz or, say, 192 kHz. Any extra sampling information is superfluous. However, due to benefits such as less steep cut-off filters which can lead to better sound reproduction, a variety of current professional applications and storage capacities such as DVD-Audio are using higher sampling rates to store their data.

Quantization

A process known both from audio technology and computer aided music composition. In computer aided music composition the term refers to rounding off rhythm values to whole tone multiples of the beat speed (tempo) or other specified rhythm value, and serves the improvement of musical timing. It is a process which records or changes temporal phenomena of acoustic music.

Quantization Error

Quantization Error occus when the A/D converter tries to quantize a signal that is too quiet. When quantizing, the converter rounds decimels to the nearest whole bit. If the acoustic signal level equals anywhere from 0.5 to 1.49 Volts, it is quantized as 1 Volt. If the acoustic signal level equals anywhere from 0 to 0.49 Volts, it is quantized as 0 Volts. That original acoustic signal is never quantized and is therefore lost. Quantization error = 1/2LSB (Least Significant Bit) The higher resolution you quantize at, the less noticeable the quantization error. For example: If you quantize at 1 bit: -The LSB is 1 Volt and thus the quantization error = 0.5 Volts -The maximum resolution for a 1 bit recording is 1 Volt -The quantization error is half the maximum resolution which means that 50% of the original recording is vulnerable to quantization error. If you quantize at 2 bits: -The LSB is 1 Volt and thus the quantization error = 0.5 Volts -The maximum resolution for a 2 bit recording is 3 Volts -This leaves 16.67% of the original signal vulnerable to quantization error. This obviously has a lot to do with the dynamic range of the original acoustic signal. If the signal is always at least 1/2LSB, the signal will always be quantized, and no information will be lost.

Digitization

Dither

Noise-shaping

Jitter

For more information, please see the Wikipedia article Jitter.

Methods of digital encoding

Pulse-code modulation

The most common method of creating digital audio is Pulse-code modulation (PCM). PCM digital audio is typically sampled at 44.1 kHz for CD recordings, or higher for professional audio applications. For comparison, speech signals for telephony are only sampled at 8 kHz. Higher sample rates for professional recording are becoming popular. These include 88.2 kHz, 96 kHz, and 192 kHz. The amplitude of each sample is a numeric value that is represented by a certain number of bits. The more bits that are used to represent the amplitude, the greater the dynamic range that can be represented, with each bit providing a gain of approximately 6 dB. The dynamic range of 16 bit digital audio is therefore approximately 96 dB, whereas the dynamic range of 24 bit digital audio is 144 dB. 8 bit digital audio has a dynamic range of approximately 48 dB. The amount of data created by digital audio is quite large. 16 bits per sample at 44.1 kHz creates 705600 bits per second (8 bits = 1 byte). Thus for a stereo recording, approximately 10 MB will be generated per minute. 24 bit, 96 kHz digital audio has a bit rate of 2304000 bits per second, or around 33 MB per minute for stereo. Due to this, different forms of audio data compression have recently become more popular. Another method of creating a digital representation of the audio waveform is Direct Stream Digital or DSD. The Super audio compact disc uses this format. Since digital audio, unlike analog audio, is always accompanied implicitly or explicitly by a sample clock, synchronization is a crucial consideration in digital audio systems. This is usually accomplished by genlocking all the systems in a facility to a single master audio clock. Plesiochronous operation is not advisable, as it tends to result in widespread hard-to-debug problems.

Digital audio technologies

- Digital audio tape (DAT)
- DAB (Digital Audio Broadcasting)
- Compact disc (CD)
- DVD
- Minidisc
- Super audio compact disc
- Digital audio workstation
- and various audio file formats

Digital audio interfaces and interconnects

- AC97 (Audio Codec 1997) interface between Integrated circuits on PC motherboards
- ADAT interface
- AES/EBU interface with XLR connectors
- AES47, Professional AES3 digital audio over Asynchronous Transfer Mode networks
- I2S (Inter-IC sound) interface between Integrated circuits in consumer electronics
- MIDI -- low-bandwidth interconnect for carrying instrument data; cannot carry sound
- S/PDIF, either over coaxial cable or TOSLINK Audio signals can also be carried losslessly over general-purpose buses such as USB or FireWire.

External links

- [http://www.dmalham.freeserve.co.uk/adat.html Information on the ADAT interface]
- [http://www.studioathome.com Home audio recording forum] Category:Audio engineering
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Bing Crosby

Harry Lillis "Bing" Crosby (May 3, 1903 – October 14, 1977) was one of the most popular and influential American singers and actors of the 20th century whose career flourished from 1926 until his death in 1977. In terms of his influence on music and popular culture he is rivaled only by Elvis Presley and The Beatles. Known for his large range, rich baritone and vibrant, clear enunciation, Crosby is considered one of the finest vocalists ever, and is credited as being the inspiration for the likes of Frank Sinatra, Perry Como, Dean Martin and more recently Michael Bublé. In 1992, Artie Shaw offered his opinion of Crosby's place in American culture in these terms: "The thing you have to understand about Bing Crosby is that he was the first hip white person born in the United States"¹. In 1962 Crosby was the first person to receive the Grammy Lifetime Achievement Award.

Early Life

Harry Lillis Crosby was born in Tacoma, Washington on May 3, 1903 in a house that his father built (1112 North J Street, Tacoma, Washington). His family later moved to Spokane, Washington in 1906 to find work. He was the fourth of seven children - five boys Larry (1895-1975), Everett (born 1896), Ted (born 1900) and Bob (1913-1993) and two girls Catherine (born 1905) and Mary Rose (born 1907) - born to English-American Harry Lowe Crosby (

Digital photography

History

Sensors

Multifunctionality and connectivity

Performance metrics

Pixel counts

Possible problems

Applications and considerations

Sensor size and angle of view

File types and data storage formats

Digital camera backs

Comparison with film cameras

Advantages of digital: consumer cameras

Advantages of digital: professional cameras

Disadvantages of digital cameras

Equivalent features

A comparison of frame aspect ratios

Market impact

Social impact

See also

External links

Photography

Photographic image forming devices

Uses of photography

History of photography

Invention

Chemical photography

Reference

Social history

Popularization

Economic history

Color photography

Digital photography

Commercial photography

Terminology

Photography as an art form

Aesthetic realism and photography

Reference

Additional reading

See also

Basic topics in photography

Photographers

Photographs

Historical

Techniques

Photographic products

Other

External links

Photographic film

Film basics

History of film

Special films

Common sizes of film

Companies that manufacture photographic film

See also

Sensor

Overview

Classification of types

Thermal energy

Electromagnetic sensors

Mechanical sensors

Chemical sensors

Optical and radiation sensors

Ionising radiation

Non ionising radiation

Acoustic sensors

Acoustic

Other types of sensor

Non Initialized systems

Initialized systems

Classification of measurement errors

Biological sensors

See also

Links

Digital audio

Technology overview

Sampling

Quantization

Quantization Error

Digitization