Chapter 4 — Question 2

Consider a (monochrome) black-and-white film. What determines the general sensitivity
of this film and why is it important?

Answer

The general sensitivity is a measure of how much light energy is required to
bring about a change in film density. It is determined by the size of the silver
grains in the light sensitive emulsion. It can be increased by sensitisation, which
is the addition of small chemicals such as gold or sulphur. The higher the sensi-
tivity (or film speed) the less bright an object needs to be in order to be recorded
upon a film.

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