Tonal range


The tonal range, also known as the subject luminance range or brightness range, is the difference between the maximum (highlights) and minimum (shadows) amounts of light reflected from a subject. This is measured as a ratio e.g. 100:1.

The tonal range is used in calculating the exposure and development needed to record the scene accurately. This is achieved by plotting the maximum and minimum subject luminance on a film’s characteristic curve. The exposure should then avoid compression in the non linear areas of the film’s curve.