The Canon EOS Digital Rebel XSi/450D Companion

CHAPTER 6

CHANGING ISO

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Remember, a stop is one doubling of exposure. If we’re shooting with the 18-

55mm at full telephoto, then we’re shooting at an equivalent focal length of

88mm. is means that we shouldn’t try to handhold with a shutter speed below

1/88th of a second. But, with three stops of stabilization, that works down from

1/88th to 1/44th to 1/22nd. So, in theory, you can shoot with that lens at 1/22nd

of a second when shooting at full telephoto. Whether or not you really can de-

pends on how steady you are at holding the camera.

Why would you want to shoot this slow? Well, sometimes you’ll be shooting in

situations that are so dark that you’ll have no choice. You’ll need to open the lens

all the way and shoot at a very slow shutter speed. So, the slower you can manage,

the better the chance of getting the shot. We’ll discuss low-light shooting in more

detail in Chapter 9.

Objects in your scene that are moving might still be blurry when shooting with

such a slow speed, but you shouldn’t see an overall softening of your image due

to camera shake.

REMINDER: Steady As She Goes

When trying to hold the camera steady—which is especially important when

using a slow shutter speed

—remember to gently squeeze the trigger. Use the

posture tips we discussed in Chapter 1, and don’t hold your breath. Holding

your breath actually makes you shakier. If possible, tr