Digital versus film photography
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[edit] Digital versus film photography
While photographers debate over which of the two formats, digital or film, is superior, each format has advantages. This section discusses those points.
[edit] Quality
There are many measures which can be used to assess the quality of still photographs. The most discussed of these is spatial resolution, i.e. the number of separate points in the photograph. This is measured by how many millions of picture cells make up the photo.
The comparison of resolution between film and digital photography is complex. Measuring the resolution of both film and digital photographs depends on numerous issues. For film, this issue depends on the size of film used (35 mm, Medium format or Large format), the speed of the film used and the quality of lenses in the camera. Additionally, since film is an analogue medium, it does not have pixels so its resolution measured in pixels can only be an estimate.
Similarly, digital cameras rarely perform to their stated megapixel count. Other factors are important in digital camera resolution such as the actual number of pixels used to store the image, the effect of the Bayer pattern of sensor filters on the digital sensor and the image processing algorithm used to interpolate sensor pixels to image pixels. In addition, digital sensors are generally arranged in a rectangular pattern, making images susceptible to moire pattern artifacts, whereas film is immune to such effects due to the random orientation of grains.
Estimates of the resolution of a photograph taken with a 35 mm film camera vary. It is possible for more resolution to be recorded if, for example, a finer grain film is used or less resolution to be recorded with poor quality optics or low light levels. The analysis of R. N. Clark leads to this conclusion: "The digital megapixel equivalent of film is highly variable and roughly depends on film speed. Slow, fine-grained 35 mm films with speeds of ISO 50 to 100 have estimated megapixel equivalents of 8 to 16 megapixels. ISO 400 films are only around 4 megapixels." This would place top-of-the-range digital cameras (as of 2006) well over 35 mm film cameras. However, different films with the same ISO speeds can have different lines, so a direct comparison to digital is not possible.
While 35 mm is the standard format for consumer cameras, many professional film cameras use Medium format or Large format films which, due to the size of the film used, can boast resolution many times greater than the current top-of-the-range digital cameras. For example, it is estimated that a medium format film photograph can record around 50 megapixels, while large format films can record around 200 megapixels (4 × 5 inch)[1] which would equate to around 800 megapixels on the largest common film format, 8 × 10 inches.
The resolution of modern black and white slow speed film, exposed through a high quality prime lens working at its optimum aperture yields usable detail at a scanned file size of greater than 30 megapixels. With consumer 35 mm color negative film an effective resolution of over 12 megapixels is achievable and in an inexpensive 35 mm point and shoot camera a resolution of over 8 megapixels may be achieved.
When deciding between film and digital and between different types of camera, it is necessary to take into account the medium which will be used for display, and the viewing distance. For instance, if a photograph will only be viewed on a television or computer display (which can resolve only about 2 megapixels and 1.3 megapixels, respectively, as of 2006), then the resolution provided by a low-end digital cameras may be sufficient. For standard 4 × 6 inch prints, it is debatable whether there will be any perceived quality difference between digital and film. Even if the print is to be large billboard, it is not clear that the extra resolution of a medium or large format will be necessary, since they are viewed from relatively long distances. For larger prints, the extra resolution of a good 35 mm film photograph may be desirable.
It should be noted that a special case exists for long exposure photography - Currently available technology contributes random noise to the images taken by digital cameras, produced by thermal noise and manufacturing defects. Some digital cameras apply noise reduction to long exposure photographs to counteract this. For very long exposures it is necessary to operate the detector at low temperatures to avoid noise impacting the final image. Film grain is not affected by exposure time, although the apparent speed of the film does change with longer exposures.
[edit] Convenience and Flexibility
This has been one of the major drivers of the widespread adoption of digital cameras. Before the advent of digital cameras, once a photograph was taken, the roll of film would need to be finished and sent off to a lab to be developed. Only once the film was returned was it possible to see the photograph. However, most digital cameras incorporate an LCD screen which allows the photograph to be viewed immediately after it has been taken. This allows the photographer to delete unrequired photographs and offers an immediate opportunity to re-take. When a user desires prints, it is only necessary to print the good photographs.
Another major advantage of digital technology is that photographs can be conveniently moved to a personal computer for modification. Many professional-grade digital cameras are capable of storing pictures in a Camera RAW format which stores the output from the sensor directly rather than processing it immediately to an image. When edited in suitable software, such as Adobe Photoshop or dcraw, the photographer can manipulate certain parameters of the taken photograph (such as contrast, sharpness or color) before it is "developed" into a final image. Less sophisticated users may choose to simply "touch up" the actual content of the recorded image; software with which to do this is often provided with consumer-grade cameras. (See Digital image editing.)
Film photographs may be digitised in a process known as scanning. They may then be manipulated as digital photographs.
[edit] Price
The two formats (film and digital) have different emphases as regards pricing. With digital photography, cameras tend to be significantly more expensive than film ones, comparing like for like. This is offset by the fact that taking photographs is effectively cost-free. Photographs can be taken freely and copies distributed over the internet free of charge.
This should be contrasted with film photography where good-quality cameras tend to be less complicated and, therefore, less expensive. But this is at the expense of ongoing costs both in terms of film and processing costs. In particular, film cameras offer no chance to review photographs immediately after they are shot, and all photos taken must be processed before knowing anything about the quality of the final photograph.
There are costs associated with digital photography. Digital cameras use batteries, some of which are proprietary and quite expensive. While they are rechargable, they do degrade over time and must be periodically replaced. Although there is no film in digital cameras, there is the requirement to store the images on memory cards or microdrives which also have limited life. Additionally, some provision for storage of the digital image must be made. In general this would be either an optical disc produced by a shop or photofinisher, or by the photographer on a computer system. If physical prints are to be made they can either be purchased from a photofinisher, or produced by the photographer.
The price differential between the two formats is often dictated by the intent of the photographer and the purpose of his or her work.
[edit] Robustness
Film has advantages over digital, at least with current technology. One main advantages is latitude, or the ability to produce a good image from over- or underexposed negatives. Slightly overexposed digital images can lose all data in the highlights, and underexposed images will lose significant shadow detail. Photographers can over- or underexpose film, especially black and white film, and still produce normal images.
Dust on the image plane is a constant issue for photographers. Digital cameras are especially prone to dust problems because the sensor is static, and for digital SLRs dust is difficult to rectify. Some digital SLRs however, have systems that remove dust from the sensor by vibrating or knocking the sensor. Some cameras do this in conjunction with software that remembers where dust is located on the sensor and removes dust-affected pixels from images.
[edit] Archiving
When choosing between film and digital formats, it is necessary to consider the suitability of each as an archival medium.
Films and prints processed and stored in ideal conditions have demonstrated an ability to remain substantially unchanged for more than 100 years. Gold or platinum toned prints probably have a lifespan limited only by the lifespan of the base material, probably many hundreds of years.
The archival potential of digital photographs is less well understood since digital media have existed for only the last 50 years. There exist three problems which must be overcome for archival usage: physical stability of the recording medium, future readability of the storage medium and future readability of the file formats used for storage.
Many digital media are not capable of storing data for prolonged periods of time. For example, magnetic disks and tapes may lose their data after twenty years, flash memory cards even less. Good quality optical media may be the most durable storage media for digital data.
It is important to consider the future readability of storage media. Assuming the storage media can continue to hold data for prolonged periods of time, the short lifespan of digital technologies often causes the drives to read media to become unavailable. For example, the first 5¼-inch Floppy disks were first made available in 1976. However, the drives to read them are already extremely rare just 30 years later.
It must also be considered whether there still exists software which can decode the data. For example, many modern digital cameras save photographs in JPEG format. This format has existed for only around 15 years. Whether it will still be readable in a century is unknown, although the huge number of JPEG files currently being produced will surely influence this issue.
Most professional cameras can save in a RAW image format, the future of which is much more uncertain. Some of these formats contain proprietary data which is encrypted or protected by patents, and could be abandoned by their makers at any time for simple economic reasons. This could make it difficult to read these 'raw' files in the future, unless the camera makers were to release information on the file formats.
However, digital archives have several methods of overcoming such obstacles. In order to counteract the file format problems, many organizations prefer to choose an open and popular file format. Doing so increases the chance that software will exist to decode the file in the future.
Additionally many organizations take an active approach to archiving rather than relying on formats being readable decades later. This takes advantage of the ability to make perfect copies of digital media. So, for example, rather than leaving data on a format which may potentially become unreadable or unsupported, the information can typically be copied to newer media without loss of quality. This is only possible with digital media.
And, of course, the digital images can always be printed out and saved like traditional photographs although there are few , if any, commercial services available producing true silver halide prints from digital sources. All dye based prints, as noted above, have only limited permanence.
[edit] Integrity
Film produces a first generation image, which contains only the information admitted through the aperture of the camera. Film "sees" in color, in a specific spectral band such as orthochromatic, or in broad Ppanchromatic sensitivity. Differences in development technique can produce subtle changes in the finished negative or positive, but once this process is complete it is considered permanent.
Film images are very difficult to fabricate, thus in law enforcement and in cases where the authenticity of an image is important (passport or visa photographs), film provides greater security over digital, which has the disadvantage that photographs can be conveniently moved to a personal computer for modification.
