The length of time the plate is exposed to light. The length of time the light has to “sink in”. It’s measured in seconds, or most commonly, fractions of seconds. The longer the exposure, the more light hits the plate, and therefore, the brighter the resulting picture.

If there is a lot of light, such as a sunny, outdoor setting, then the exposure needs to be short. If overexposed, the light portions of the shot will be pure white and the detail will be lost. In extreme cases, the shot might come out solid white. If it’s getting dark, if it’s past dark, if you’re indoors, then you’ll have the opposite dilemma. Read more…