Last Monday Ray gave an excellent talk on histogram curves and how they aid with obtaining the correct exposure for a given scene. He also provided some cards to illustrate the effects of the three variables that influence exposure in photography, Shutter Speed, Aperture settings and ISO settings. A fourth card shows how the histogram on your camera can provide information on the exposure you have set to enable you to judge where the detail will be in the final image.
These can be printed out by copying each image in tun and pasting into a word processor for resizing and printing.
Published here with Rays permission