groping in the dark

Let the Light Shine In

When you're working in manual mode with your camera, you've not only got to worry about getting the right shot, you also have to fiddle with your camera settings, keeping everything in balance so that you end up with a good exposure. One of these settings is your camera's aperture, or f-stop: the opening in the lens that controls the amount of light coming into the camera. The lenses for many 35mm cameras have aperture settings that range from something like f/4 to f/22. The higher the number, the smaller the aperture opening is.

Confusion alert: to "stop down" a lens means to close it, thus the aperture number goes up, not down. Got that?...No? Okay, if I change my aperture from f/4 to f/5.6, I have moved down one full stop. Someday, I'll post an entry explaining where all the arcane numbers come from and why everything seems backwards, but for now, just try to learn that as far as aperture sizes go, 22 is smaller than 4.

I have seen 35mm lenses that have apertures as small as f/32 and others as large as f/1.4. Lenses with large apertures (such as f/1.4) are known as fast lenses and are usually much more expensive than your average lens that may only go as big as f/4. Faster lenses, with their large openings allow for faster shutter speeds or for working with less available light. I have a 35mm-80mm zoom lens that has a maximum aperture of f/4.5 while my 19mm-35mm lens is faster by one full stop at f/3.5. It may not sound like much, but that one stop makes a big difference in the shots that you will be able to get. When shopping for lenses, all other things being equal (which, let's face it, they never are), get the fastest lens you can afford.

The other thing that your aperture controls is the depth of field in your shot. With a wide aperture, you will have a shallow depth of field. The narrower the aperture, the greater the depth of field. Which aperture you pick totally depends on the kind of shot you are taking. The typical examples given are portraits vs. landscapes. For portraits, you want a fairly shallow depth of field where the camera is focused on the subject and the background fades away into blurry soft focus, thus concentrating your attention on the subject. In landscapes, you are usually interested in keeping everything in sharp focus, both the foreground and background. Ansel Adams, in his stunningly sharp and detailed landscape photography, typically used extremely narrow apertures.