iMagE STabilizaTion

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AFSET

ISO

The Canon Magazine 91

ALL ABOUT SHUTTER SpEEd

Modes 1 and 2 Mode 1 Image Stabilization

is for handheld photography,

while Mode 2 is used for panning

Mode 3 Mode 3 only actuates IS when the shutter is fully pressed, so the image in the viewfinder moves more naturally

hen it comes to getting a sharp shot at slower

shutter speeds, Canon’s Image Stabilization system (or third-party lens makers’ equivalents) is a huge help.

IS detects camera shake and compensates for it. When you press the shutter button, tiny gyroscopes inside the lens sense any shake and pass this on to a microcomputer that moves a special group of lens elements to correct for it.

What goes on under the hood is of less importance to us as photographers, but what’s vital is that IS can help you gain up to four stops – so if you shoot at 1/30 sec with IS engaged, you are shooting at the equivalent of 1/500 sec.

A couple of words of warning – IS isn’t foolproof and can’t perform miracles. It won’t guarantee you sharp, handheld shots at very slow speeds, such as 1/8 sec. Success will still depend on your technique and the focal length you are using. It has no impact on subject movement either – so if your shutter speed is too slow for the subject, your shot still won’t be sharp!

The longer the focal length you use, the more your shot is susceptible to camera shake

too, so you have to compensate by keeping shutter speeds higher. An oft-quoted rule of thumb is to use a shutter speed that, at a bare minimum, is roughly equal to the focal length of the lens.

You will also often hear advice that says that IS should be switched off when the camera is on a tripod. For very

long exposures, particularly with older lenses, this is good advice, but many newer lenses will sense tripod use and automatically disable IS. If you are shooting with a long lens on a tripod and moving the lens to track a subject, then keep IS on as it will definitely help.

Many telephoto lenses have two Stabilizer modes. Keep the

lens in Mode 1 if you are using the camera normally but, if you are panning, switch to Mode 2; the lens will then detect the direction of movement and disable IS accordingly. Some high-end lenses also have a third IS mode. In IS Mode 3 the IS system only becomes active when the shutter button is fully depressed.

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Keep it steady for sharp shotsHow lenses with built-in stabilization can make a vital difference

School tip: Mirror LockupStop avoidable vibration spoiling a long exposureALThough NEgLIgIbLE there is the potential that vibration caused by the internal mirror moving up just before an exposure is made can cause loss of critical sharpness; this is most evident in long-exposure landscapes or macro photography.

The answer is to lock the mirror up before the image is taken. When you enable the Mirror Lockup function,

you have to press the shutter release twice; once to flip the mirror out of the way, and again to take the shot (you’ll need to use a remote release to avoid jogging the camera, or the 2-sec Self-timer function). The delay before the image is taken will allow the vibrations to settle. Alternatively, if you shoot in Live View, the mirror is already flipped out of the way.