Memorize This!

12 essential facts, formulas, and photographic rules

What happens when your systems go belly-up, when all of that cutting-edge technology dies and you must rely on (gasp!) your own knowledge? It pays to have these basics in your head. They can get you out of a jam and help you get good shots when nothing else will.
1. Sunny 16 rule The basic exposure for an average scene taken on a bright, sunny day is f/16 at a shutter speed equivalent to one over the ISO setting—that is, f/16 at 1/100 sec at ISO 100. From this you can interpolate, and try f/22 at the beach, f/11 on a cloudy-bright day, etc.

2. Moony 11, 8, and 5.6 rules There are many different rules that work well when shooting the moon. One favorite for a proper exposure of a full moon is f/11 at one over the ISO setting. For pictures of a half moon, use the same shutter speed at f/8, and for a quarter moon, use the same shutter speed at f/5.6.

3. Camera shake rule The slowest shutter speed at which you can safely handhold a camera is one over the focal length of the lens in use. As shutter speeds get slower, camera shake is likely to result in an increasing loss of sharpness. So, if you're using a 50mm lens, shoot at 1/60 sec or faster. Not enough light? Use a flash, tripod, or brace your camera against a solid object.

4. Anatomical gray card Metering off an 18-percent neutral gray card is a good way to get a midtone reading that will give you a good overall exposure of a scene. Forgot your gray card? Hold your open hand up so it's facing the light, take a reading off your palm, open up one stop, and shoot. (Various skin tones rarely account for even a full-stop difference.)

5. Depth of field rules When focusing on a deep subject, focus on a point about a third of the way into the picture to maximize depth of field, because the depth-of-field zone behind that point is about twice as deep as the depth-of-field zone in front of it. This works for all apertures and focal lengths, but the smaller the aperture and the shorter the focal length, and the greater the distance you shoot at, the greater the depth of field.

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