Black and white emulsions and Slides: Digital Cameras Basic Theories

Slides
Reversible black and white material is used mainly for audiovisual productions, print reproduction, engravings or projection copies, also to archive documents or press. They are usually low sensitivity materials, with high characteristic contrast and a narrow exposure latitude. Therefore the technical exposure has to be very precise and the contrast of the scenes that can be registered with detail is much less than with negatives.

Orthochromatic Emulsions

Until now we have considered that all black and white emulsions are sensitized to all visible colors, in a way that the correspondence between the apparent brightness level and the density level on the print is

proportional for any color ( panchromatic emulsions). Nonetheless, the emulsion's sensitivity to different types of light can be modified depending on your needs. In black and white, the emulsions used in the dark room respond only to blue and green colored light, while they aren't sensitive to red and yellow ( orthochromatic emulsions). This lets us manipulate the sensitive material with a safety light of this color, since the printing of a monochrome negative can be done only with the blue part of the light projected by the enlarger.