Which statement describes reciprocity failure in film?

• A. Increased film density with longer exposure times
• B. Decreased film sensitivity at long exposure times
• C. No effect
• D. Affects only high-speed film

Answer: (B)

Reciprocity failure means the film’s response to exposure isn’t proportional when exposure times are extended. For long exposure times, the chemical reactions that create the latent image don’t keep up, so the film becomes less sensitive and requires more exposure than a simple linear model would predict to reach the same density. That’s why the statement describing decreased film sensitivity at long exposure times is correct. The other ideas don’t fit: the issue isn’t that density simply keeps increasing with exposure in a straightforward way, there’s a breakdown of the expected proportionality; there is an effect to some degree, not none; and reciprocity failure isn’t limited to high-speed films, though it tends to be more noticeable there.