How To Buy A Camera
Where and how you will use your camera are considerations as important as its features
"Which camera should I buy?” When you’re an editor of a photo magazine, you get this question a lot. The asker wants you to respond with a specific make and model (as if there’s only one “good” camera that insiders know) and is disappointed when you answer the question with more questions.
What do you shoot? How often? How will you use the photos? Buying a camera is a lot like buying a car. There are several classes of cameras to consider, and cross-over between the classes can blur the lines. The first questions to answer really are about yourself, before you start comparing specifications.
Do you need an SLR?
There’s no question that interchangeable-lens cameras are the best choice for speed, creative control and image quality. You’ll notice the speed difference right away. With most compact cameras, you’ll wait a few seconds on startup for the lens to extend; interchangeable-lens cameras don’t have this delay—just take off the lens cap and you’re ready to shoot.
Another speed difference is shutter lag: the time between when you push the shutter release and when the image actually is taken. A pro SLR will have a shutter lag of around 16 milliseconds, or about 1⁄60 of a second. Compare that to a typical compact camera, which can have a lag of 1⁄4 of a second or more—15 times longer. If you’re shooting still subjects, like landscapes or posed portraits, this may not be a problem; but for sports-action and candid photography, where capturing the “decisive moment” is essential, you have a much better chance with an SLR.
Part of the speed difference is in the autofocus system. Almost all compact cameras use contrast-detection AF. With this method, the imaging sensor also serves as the autofocus sensor. The system evaluates the contrast of the scene, finds the focus point where it detects the greatest contrast and locks focus there. This process requires multiple readings.
SLRs typically use phase-detection AF (except when in Live View mode). Phase-detection AF employs an additional sensor dedicated to focusing. A portion of the light coming through the lens is reflected, then split into two separate beams that strike the AF sensor. The sensor can immediately determine correct focus based on how the two beams strike it. Since only a single reading is needed, these systems are much faster than contrast-detection AF.
So, if speed really is important for your photography, an SLR is the better choice. It’s also the more adaptable camera type, thanks to the ability to swap lenses. Most compact cameras today offer decent optical zooms, but their range usually is moderately wide to moderately telephoto. For ultrawide and extreme-tele range, or specialty lenses like tilt/shift and macro, an SLR gives you access to a bigger world of creative options.