PHOTOGRAPHY FROM THE BEGINNING LESSON 1 - CONTD

Actually, that brings us to another important thing: it's not just subject motion that you want to stop—there's also camera motion. If you've ever shot a gun, you know that it's impossible to hold something completely steady. If you've shot a gun with a scope, which essentially magnifies your gun sights, you know that as you zoom in your body's shakiness is even more apparent. You can improve things by resting your gun on something steady or even changing your posture.

One of the worst positions is both hands out in front of you holding, say, a handgun. With cameras, it's the same. No matter how steady you try to be, your body is always making minute twitches that will ruin pictures with a long enough shutter speed. How long is "long enough?" That depends on how steady you are and your position (holding a point and shoot out in front of you like a handgun is, like with guns, one of the worst positions—even holding the camera against your head helps).

A conservative rule of thumb for most of the smaller-frame digital SLRs (ones with sensors called APS-C) is to always have a shutter speed that is 1/2f or faster (if you can afford a full-frame SLR, use 1/f instead). For example, if you're taking a shot at 50mm you want a shutter speed of at longest 1/100. This is conservative, though, so you have to experiment to see what fraction of pictures turn out for you at slower speeds and then you can decide how close to the edge you want to live. The best way to reduce camera shake is to put the camera on a good tripod, but lots of new cameras and lenses also have other ways to reduce it.

There are two main types of image stabilization: optical and sensor-based. Canon and Nikon favor optical image stabilization (their sytems are called IS and VR, respectively) and most of the other companies favor sensor-based stabilization. With optical image stabilization, there is a little accelerometer in the lens (like the motion sensor in a Wii remote) that monitors the way the lens is shaking. That information is used to actually move one of the lenses inside the lens to keep the image on the same spot of the sensor while the shutter is open.

The sensor-based IS is similar, but instead of moving a lens, the sensor itself is moved around to counteract the shake. The most important thing to remember about any image stabilization system (including tripods) is that even though you can reduce camera motion, it doesn't do anything about subject motion. This is why pros will still buy really fast lenses: if you need fast shutter speeds, IS can still be useful but the bottom line is you need a wide aperture (or fast film, and that's the next thing I'll write about).