Zoom easy

When you read the specs for a camcorder—or read the logos painted on its body— you frequently encounter numbers like “12X/300X ZOOM!” The number before the slash tells you how many times the camera can magnify a distant image, much like a telescope. That number measures the optical zoom, which is the actual amount that the lenses themselves can zoom in. Such zooming, of course, is useful when you want to film something that’s far away. You should know, however, that the more you’ve zoomed in, the shakier your footage is likely to be, since every microscopic wobble is magnified by, say, 12 times. You also have to be much more careful about focusing. When you’re zoomed out all the way, everything is in focus—things near you, and things far away. But when you’re zoomed in, very near and very far objects go out of focus. Put into photographic terms, the more you zoom in, the shorter the depth of field (the range of distance from the camera that can be kept in focus simultaneously).