Four Handy Photo Rules

Follow these rules of thumb to take better pictures and get more reliable results.

It's not expensive gear or fancy software that separates great photographers from ordinary ones. After all, even $200 pocket-sized digital cameras are more advanced than the contraptions that Ansel Adams used to take his famous photos 50 years ago.

No, it's not equipment: Knowledge is what makes a great photographer. As any photographer will tell you, there are a million little rules of thumb that can come in handy at the most unexpected moments. This week I've got four gems that you can store away for the right moment.

You might wonder how big you can safely print a digital photo. This is where a little long division goes a long way. Just take the pixel dimensions of your photo and divide by 200. The result is the size, in inches, you can print on a typical inkjet printer.

Last week, I wrote about controlling motion blur and its mean-spirited cousin, camera shake. To reduce blur from camera shake, I recommended that you use a tripod or set your camera to a fast shutter speed. But what shutter speed?

As a general rule, the slowest speed that you can use reliably while hand-holding your camera is equal to the reciprocal of your focal length. If you're using a 100mm lens, for instance, you'll need to shoot at 1/100 second or faster. 50mm? You can probably get away with a rather slow 1/50 second.

ReadCapturing Subjects on the Movefor more on using ISO.

You probably know that your camera's built-in flash is not especially powerful; it can throw light only about 10 feet or so (check your camera manual for the exact range). But you might not realize that increasing the camera's ISO can extend the flash's range.

ISO is a measure of the camera sensor's sensitivity to light, and most cameras let you dial up the ISO for taking better pictures in low light--with the trade-off being more digital noise in your shots.

Here's the secret: To double the range of your flash, quadruple the ISO. So if your flash has a 10-foot range, but you're shooting across a 20-foot room, change the ISO from 100 to 400.

ReadTake Better Flash Photosfor more tricks.

You are probably familiar with the concept of depth of field. When you pick a point in your photo to be in sharp focus, there's a region in front and behind that location that's still sharp.

The depth of field size varies depending upon the focal length of the lens and the distance from the camera to the subject, but one thing always remains true: There's always about twice as much depth of field behind the point of focus as there is in front.