Black and white chromogenic films like Kodak 400CN allow you to shoot black and white images that can be developed conveniently with C-41 color processing. That means you can get black and white results on color negative paper from your local pharmacy rather than sending off to a specialist.

These films work like any other C-41 film; development causes dyes to form in multiple emulsions that coat the film base. In color film each layer is only sensitive to a certain color of visible light. However, the C-41 black and white film structure is different. Although there are multiple layers, each is sensitive to all colors of light, and are designed to produce a black dye, resulting in a black and white image.

There can be some color tint from the processing which can be good or bad depending on your preference and what you want to achieve, but the results are not true black and white. The film is incredibly sharp with very fine grain, and a convenient and cheap alternative to black and white proper.

The film responds in the same way as traditional black and white film when using color filters.