10 July 2008

Canon Image Stabilizer (IS)

Some words about Canon Image Stabilizer Lens (IS in short). Other manufactures have similar technology, but with different names (for example: VR (Nikon), OS (Sigma)). Some manufactures use stabilizer in their camera (not in lens). This sounds pretty good while we have stabilizer at capturing with all lenses. Although idea isn’t bad, this stabilization isn’t so good like this in Canon IS lens. Canon also has the biggest number of IS lenses available and Canon IS has a reputation for good stabilizer.

Why stabilizer?
While we capturing an image with our camera, sharpness of image depends on some things. One of most important is how stable was camera at the time, when shutter was opened. The longer this time is, more probably we will ruin our image.
One old and simple rule is – use time shorter then 1/(focal length in mm). For example – if you have 50mm lens, use shutter time shorter than 1/50 s, and if you have 200 mm lens, you should use shutter time shorter than 1/200 s. Usually this can work if we have good lightness and/or using open apertures.
The best solution is using solid tripod and cable release. Then you can take an image where shutter is open some minutes – not just hundreds of second. But solid tripod is heavy and clumsy. And we don’t want to have a trekking with some additional weight.
In this case image stabilizer can help. You can’t expect miracles, but sometimes results are almost like miracle.

How it works?
In one word – complicated. Image stabilizer uses sensors, gyros, optical correction system and microcomputers. With information from sensors and gyros, all this can enable reliable and accurate camera shake correction.
Pressing the shutter release half way engages the image stabilizer. You hear quiet hum and the viewfinder image becomes still. It works some seconds and if you don't press shutter, stabilizer will turn off.

What lenses are available?
There are many lenses with image stabilizer available. From standard and telephoto zoom lens to fixed focal length lens. Some cheap (also in kit lens) and some (very) expensive.
I use 70-200 f4 IS and 24-105 f4 IS. Both are very good lens with image stabilizer as big plus.

Using on tripod
If Image Stabilizer corrects camera shake, this can cause vibrations if camera (lens) is on tripod. Newer lenses can actually sense and account a tripod (Canon calls it tripod detection - added in 2000). As a result you don’t need to switch image stabilization off at all.
If you don’t know if your lens has tripod detection, then it is better to turn off Image Stabilizer if your camera is on tripod.

Benefits of using lens with Image Stabilizer
Shooting in low light situations of course. With latest Image Stabilizer lens, you can handhold up to four stops to get usable picture. For example - I can get a sharp picture at 1/20 s at 200 mm.
Even if there is enough light to handhold, the picture with Image Stabilizer will be sharper.

Cons
There is no free lunch. What if object we photographing is moving? Then Image Stabilizer won’t help, because sharpness isn’t problem of handholding. But here are one exception – panning. Newer Image Stabilizer lens have two modes. First for normal use, second for panning - which turns off one axis of stabilization.

2 comments:

Patrick said...

Does that mean that when shooting a moving object, i should put the IS off

Iztok Grilc said...

If you have IS with two mode ("mode 1" and "mode 2"), than you can change from default (mode 1) to "mode 2". In this case lens will disable one axis stabilization to prevent unwanted stabilizer side effects. Someone call this "panning mode".

IS does NOT help to stop motion of a moving subject. It only helps to counteract the slight shaking of your hands. If you want to stop motion, you must use a fast shutter speed or flash, whether you're using IS or not.

Here is what Canon said:
"If the IS lens has a "Mode 2" setting, it compensates for panning by shutting off image stabilization in the direction that is parallel to the panning movement. With this system, it's entirely possible to compensate effectively for panning in any direction, even diagonally. It also makes no difference whether the camera is held horizontally, vertically, or diagonally with respect to the horizon line of the image."
So use "mode 2" for moving objects.