Black and White Photography

and thus is critical in controlling correct film exposure. In simple terms, you

need a relatively large (wide) opening in low-light conditions to allow enough

light to expose the film, and a smaller opening in brightly lit conditions so you

let in no more light than is needed. Note that your other primary control, shutter

speed, is equally important in determining film exposure.

The term f-stop refers to the size of the lens aperture. Most lenses offer a

wide variety of f-stops, sometimes set manually by the photographer and sometimes

set automatically by the camera. The terms lens aperture and f-stop are

often misunderstood and confused; lens aperture refers to the physical lens

opening and f-stop represents a measurement of that opening.

The following f-stops are among those available, although the range will

vary depending on the model of lens:

f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32

The f-stop numbers are counterintuitive. A higher f-stop number indicates a

smaller lens opening, which means that less light passes through; a lower f-stop

number indicates a larger lens opening and more light passing through. A lens

set at f/16, for example, allows much less light to pass through than a lens set

at f/2.

Setting the f-stop. Some lenses permit you to set the f-stop using numbers

printed on an aperture ring, a movable control on the lens. To set an f-stop, you

simply turn the aperture ring on the lens until it matches up with a marker, such