Exposure accuracy and ISO Sensitivity
Exposure accuracy is not much of a problem with manually-adjustable cameras where it can be easily determined (with the help of the histogram), and fixed using exposure compensation.
But exposure accuracy can be an issue with fully automatic cameras and with video cameras that offer little opportunity for post-exposure tonal adjustment.
Exposure accuracy can be measured by photographing a scene that includes any test chart with a grayscale pattern and analyzing it with Stepchart (for grayscale stepchart-only patterns such as the Q-13/Q-14), Colorcheck (for the X-Rite Colorchecker) or Multicharts or Multitest (for any chart with a grayscale pattern).
ISO Sensitivity (closely related to exposure accuracy) is a measure of a camera’s sensitivity to light. Imatest modules that analyze step charts (which may be included in color charts) display two measures of sensitivity when the incident light in Lux is entered. Details in ISO Sensitivity and Exposure Index