What is the Special-purpose monochrome films?
Line film. Some materials are made with high contrast emulsions. Available mostly in sheet films but also 35 mm, they give negatives with few or no greys at all between dense black and clear white, when processed in the appropriate high contrast developer. Line films (and the more extreme ‘lith’ films) are intended for photographing documents, pen-and-ink drawings, etc., which contain only pure black and pure white and need to be reproduced in this form. Emulsions are very slow and fine-grain, and most often have ortho sensitivity for easy darkroom handling.
You can also use line film to simplify regular images of full tonal range scenes into stark, graphic black and white. Since this sort of material only has a speed of about EI 8, and its high contrast demands absolute exposure accuracy, it is best to shoot your picture first on normal film, then reproduce this onto line film by re-photographing or printing in the darkroom.
Line negative film is also excellent for making slides of black-on-white line diagrams or text which then project as bold white-on-black images.
Films for monochrome slides. There are now few ‘off the shelf’ films yielding monochrome transparency images. Black and white positive slides can, however, still be made, using normal negative film processed in specialist chemistry kits from manufacturers such as Kodak. These can give excellent quality monochrome slides, with rich tone range, fine grain and extreme sharpness. But, as with all reversal-processed materials such as colour slides, you must get your exposure correct at the time of shooting because little adjustment is possible later.
Instant black and white print materials.
There is a limited range of monochrome instant-print materials, mainly intended for professional use. They work on the ‘peel apart’ basis and come in pack form or as individual sheets in special envelopes. Speeds range from ISO 50 to ISO 400. These are used mostly as ‘proofing’ materials to make on-the-spot lighting, layout and colour-translation previews when shooting a black and white assignment using regular film. It is a reassuring check on all your equipment before (and after) an important job. Instant material is approximately three times the cost of normal film. It also requires special camera backs or film holders and separate processing devices in some cases. Lastly the prints tend to have a fairly limited life, although the monochrome negatives that were available on a couple of Polaroid films, have good life expectancy.