Complete the account of contrast control.

The oldest instruction in black-and-white work is: expose for the shadows and develop for the highlights. A development shortened to squeeze a subject range by one zone is written as N−1. High dilution with minimal agitation gives a compensating effect, in which the developer exhausts locally in the highlights. A negative with detail everywhere that prints flat and grey has been under-developed.

The last blank is the diagnosis students most often reverse. A flat negative with full detail is under-developed and prints perfectly well on a harder paper; a contrasty negative with empty shadows is under-exposed and cannot be printed at all. Detail present means exposure was adequate, whatever the contrast looks like.