Saturday, January 20, 2007

introduction

Digital photography, as opposed to film photography, uses electronic devices to record the image as binary data. This facilitates storage and editing of the images on personal computers, and also the ability to show and delete unsuccessful images immediately on the camera itself.

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.

applications and considerations

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) the majority 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, placing them on the World Wide Web, or displaying them in digital picture frames. Digital cameras have also been integrated into many cell phones, although, because of the small lens in most of these phones, 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. A related concern in a specialized application is the use of digital photographs in court proceedings, with the added difficulty of demonstrating an image's authenticity. Film can also still be projected for viewing at a much higher optical resolution than even the best digital projectors.

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 funds for supplies and developing, although the equipment itself obsolesces less quickly and has a longer service life. 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, although film users can utilize the same technology with a film scanner. 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 or replaced frequently, and this means that a photographer needs access to electrical outlets. Digital cameras also tend to be much more sensitive to moisture and extreme cold. For this reason, photographers who work in remote areas, such as those who work for National Geographic overwhelmingly favor film SLR cameras. Medium- and large-format film cameras are also still preferred by publications insisting on the very highest detail and resolution, such as Arizona Highways.

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 they have a 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 with liquid nitrogen so as to reduce the visual noise caused by heat. Many astronomical instruments have arrays of many CCDs, sometimes totaling almost a billion pixels. Nowadays amateur astronomers also commonly use digital cameras, including the use of webcams for speckle imaging or "video astronomy".

advantages and disadvantages

Advantages of professional digital cameras

Image recycles every 3 seconds from before to after image.
Image recycles every 3 seconds from before to after image.
  • Immediate image review and deletion is possible; lighting and composition can be assessed immediately which ultimately conserves 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.
  • Digital manipulation: A digital image can be modified and manipulated much easier and faster than with traditional negative and print methods. The digital image to the right was captured in RAW format, processed and output in 3 different ways from the source RAW file, then merged and further processed for color saturation and other special effects to produce a more dramatic result than was originally captured with the RAW image.

Recent 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 14 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. [1]

[edit] Disadvantages of digital cameras

  • Some consider the picture quality of pictures taken on film cameras to exceed that of digital pictures.
  • Some film cameras operate without batteries, as the image is stored on film rather in memory using CCD/CMOS sensors and associated electronics which require power to operate.
  • There are special types of film, such as for infrared light, that have no equivalent in commercially available digital (CCDs are sensitive to near infrared). Some digital cameras may be converted to be highly sensitive to infrared light, while other cameras can use a special filter over the lens to block available light, and make an image with only infrared (this often requires a very long exposure).
  • Film remains more admissible as evidence in court [citation needed], as it is much harder to manipulate than digital [citation needed].
  • Film has a better dynamic range. However, some newer CCDs such as Fuji's Super CCD, which combines diodes of different sensitivity, have addressed this problem. Also, software measures that selectively expose darker pixels longer exist, and could potentially enable digital cameras with infinite dynamic range.
  • Film are available in different sizes 35mm, half-format, full-format etc and the later may under right conditions generate images with higher spatial resolution.

For most consumers in prosperous countries 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. Much of the post-shooting work once done in the past by a photo lab is now done by the photographer himself. Problems some professional photographers have voiced include: editing and post-processing of RAW files can take longer than 35mm 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/he 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.

[edit] Equivalent features

  • Image noise / grain: Noise in a digital camera's image is remarkably similar to Film grain in a film camera. 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 and protected from all light during such replacement. 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 Canon EOS-1D Mark II N can achieve 8.5 frames per second which makes it the fastest digital SLR in the world; the fastest film SLR could shoot 10 frames per second. The Nikon F5 is limited to 36 continuous frames (the length of the film) while the Nikon 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, and digital images can be stored on duplicate media. This greatly reduces the risk of losing digital images, and if done correctly, digital backups are safer than film. In comparison, copying negatives or transparencies incurs additional noise and loss of detail. Negatives can however be easily converted to digital if longevity is a requirement.
  • 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 in the development stage regardless of camera settings.

common resolutions

Common photograph resolutions. Listed under the cameras column are cameras that achieve this size at their maximum.

Width Height Aspect ratio Actual pixel count Megapixels Cameras
320 240 4:3 76,800 0.1
640 480 4:3 307,200 0.3
800 600 4:3 480,000 0.5
1,280 960 4:3 1,228,800 1
1,600 1,200 4:3 1,920,000 2
2,048 1,536 4:3 3,145,728 3
2,272 1,704 4:3 3,871,488 4
2,464 1,648 3:2 4,060,672 4.1 Canon 1D
2,560 1,920 4:3 4,915,200 5
2,816 2,112 4:3 5,947,392 6
3,008 2,000 3:2 6,016,000 6 Nikon D40
3,072 2,048 3:2 6,291,456 6.3 Canon 300D, Canon 10D
3,072 2,304 4:3 7,077,888 7
3,264 2,448 4:3 7,990,272 8
3,456 2,304 3:2 7,990,272 8 Canon 350D
3,504 2,336 3:2 8,185,344 8.2 Canon 30D, Canon 1D II, Canon 1D II N
3,520 2,344 3:2 8,250,880 8.25 Canon 20D
3,648 2,736 4:3 9,980,928 10
3,888 2,592 3:2 10,077,696 10.1 Canon 400D
4,064 2,704 3:2 10,989,056 11 Canon 1Ds
4,368 2,912 3:2 12,719,616 12.8 Canon 5D
4,992 3,328 3:2 16,613,376 16.6 Canon 1Ds II

[edit] Recent research and innovation

Lighting, optics, sensors, processing, storage, and display, with software weaving them together, are all advancing. Here are a few examples.

  • 3D models can be created from collections of normal images. So you can walk around the scene, or view it from novel viewpoints. But creating the model is very compute-intensive. Microsoft's Photosynth is available with models of famous places.[3] Software to process your own images is not yet available.
  • High Dynamic Range cameras and displays are commercially available. >120dB sensors are in development. You can create your own HDR images, with a non-HDR camera, by combining multiple exposures.
  • Motion blur can be dramatically removed by a flutter shutter (a flickering shutter which adds a signature to the blur, which postprocessing can recognize).[4] It is not yet commercially available.
  • An object's specular reflection can be captured using computer controlled lights and sensors. This is needed to create attractive images of oil paintings, for instance. It is not yet commercially available, but is starting to be used by museums.

Other areas of progress include enlarged gamut sensors, software, and displays; and computer controlled lighting.

[edit] See also