Standard brightness level across images

Hi, I want to use a set of stimuli that are all of equal brightness. Is there a command/function available that will allow me to run all of my images through, and have the resulting images be of the same brightness (they will enter in at varying levels)? Thanks, Liz

[Image Analyst]

What are the images? Do they have multiple intensity levels? Are they color or gray scale? Please post an example.