This is the setting that will allow the correct amount of light into the camera to expose the film optimally for the reigning light conditions. When changing the settings on the camera for depth of field or to "freeze" the subject, the photographer must ensure that the other relevant settings are changed to ensure optimum exposure. If optimum exposure can not be achieved at a shutter speed higher than the hand speed limit, a tripod, flash or a film with a higher film speed should be used.