Commonly used terms

Aperture The lens opening which regulates the amount of light to pass through. Unit is Stop or f/number. Common ones are f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. Smaller the number larger the opening, "faster" the lens. Open up one f-stop f/4 to f/2.8 - allows double the amount of light to pass. Stop down one f-stop f/4 to f/5.6 - the amount of light is halved.

Shutter Regulates the length of time the light reaches the film to produce an image. Unit is seconds. Common ones are 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000. A change of one setting either doubles or halves the exposure. Faster shutter speed, freezes the subject; slower shutter speed blurs.

Exposure The amount of light reaching the film, resulting from the combination of the aperture used and the shutter speed set. wider aperture + faster shutter speed = smaller aperture + slower shutter speed. Numerous combinations of f-stop and shutter speed will produce same exposure. eg. f/16 @ 1/125 = f/11 @ 1/250 = f/22 @ 1/60

Film Speed The sensitivity of the film to light. Unit is ISO numbers. Common ones are 25, 50, 100, 200, 400, 800. Higher the number lesser light is required for the correct exposure. Slower the film, finer the graininess.

Depth of Field The range of apparent sharpness in a photograph. Large apertures (small f/numbers) produce limited depth of field. Small apertures (large f/numbers) increases the depth of field.