It is used to evaluate a set of images whose color management is disparate, for example with color profiles designed under different parameters or tools, or where different parameters have been introduced in the processing that affect color.
Through this test, we can study differences in tonal reproduction for a set of images, for example, images taken with different exposure or images taken with different processing formulas where different curves are involved.
Similarly we can evaluate the evolution of the noise through images taken with different ISO to discern which ISO setting is more efficient for our equipment. It can also be used to evaluate the noise resulting from different noise reduction filters.
It is used to extract a sensitometric curve, i.e. to relate exposure settings to the intensity taken by the resulting pixels. These curves can be made by keeping the aperture fixed and varying the speed, or vice versa, but we can also make them for light sources that have intensity regulation such as flashes or LED panels. Another frequent use is for the study of the stability of flashes, so that several shots can be taken at the same power and see if they develop the same intensity or make a curve along all the steps of "power" available in our equipment and verify the linearity of it.