ISO (International Organisation for Standards) is also the Film speed in photography. Film speed is the measure of photography film’s sensitivity to light. Film with lower sensitivity (lower ISO) requires a longer exposure and is thus called a slow film, film with higher sensitivity (higher ISO) can shoot the same scene with a shorter exposure and is called a fast film.

Some links on ISO:

• wiki: film speed
• photoxels
• digital photography school
• photography basics
• all things photography
• dpchallenge

Some measurements of ISO:

• 100: low ISO
• 400 and above: high ISO