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Film vs Digital Imaging
Film - Part III - Specialty Film High Contrast black and white film is extremely slow (indicating extremely fine grain) and can be processed to give extremely contrasty images (black and white only), limited tonal range (maybe 2 levels of grey between black and white) or as very high resolution continuous tone film. Two examples would be Kodalith and Technical Pan. These films are also used in film making for titles.Low Contrast black and white film is most often used in darkroom processes. For example, to mask an extremely contrasty colour image to make it look or print more normally.
Red Insensitive films are another black and white specialty film that gives a special look as well as having the property of being able to developed by inspection using a red safelight. Most other films are panchromatic (meaning sensitive to all light) and can not be observed while processing is going on.
Infrared sensitive film can be completely insensitive to visible light or partially sensitive to visible light but predominantly sensitive to infrared (heat). This film is used for technical photography or special effects. It also allows us to see information that we can not see with the naked eye.
Ultra-violet sensitive film also allows us to see information that we can not see with the naked eye but at the other end of the spectrum.
Chromogenic film is a hybrid film that has two unique characteristics: it has very wide exposure latitude (with a fine grain structure) and is a monochrome film that can be processed in C-41 colour chemistry. This film is manufactured like colour film with two layers of emulsion: one slow and one fast. When the film is developed, as with colour film the silver images are bleached out and replaced with dyes. The combination of the two layers covering both fast and slow gives you an image that is relatively grain free and able to shoot in both low and bright light. An example is Ilford XP-1.
There is another specialized black and white film that is used to film high speed images of explosions that has three layers of emulsion. The layers are extremely slow, slow and fast. This film can record images from the time that first light is emitted right up through the very bright flash of the explosion. This film is processed as a silver image.
Processing: All films have one or more processes that are designed to deliver repeatable results for the films intended purpose(s) and to the close specification of the manufacturer. But photographers through experimentation and experience have made these material do things that are outside the specifications. Two classic examples are: overexpose/underdevelop and cross process.
When you overexpose and underdevelop a black and white film you extend the range of tones that the film can record so that the subtle patterns in the clouds are still visible but the details of the dog in the shadow of the wagon are still visible too ... normal processing could have lost one or both of those details. This now makes the negative more difficult to print but makes a beautiful print when complete.
Cross processing is just processing in the process designed for another film. Processing negative film in reversal film chemistry or vice versa produces odd result that are often used as special effects. There are literally millions of possibilities but there are only a few which are tried and true.
Posted July 22, 2004
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The next segment describes Digital Stills.
