How does IS work exactly?

Hello,

If someone can clarify this biz about the 3 stop advantage, that will be great... im thinking, if i shot in 1/30 speed, is that the equivalent to 1/60 or something?

Or links to discussions in other threads will be great. Cheers.

What IS (Image Stabilization) does is detect and compensate for lens movement by moving a little correction lens around internally. The detection of lens movement is done with little gyroscopes inside the lens.

The advantage of IS is only related to reducing blur due to your not holding the camera/lens still. If you are shooting a photo of something that is not moving and you have IS turned on, you should be able to have a comparably sharp image with the shutter speed two to three stops slower than if you were not using IS.

IS will not do anything at all for movement of the subject itself. In other words, if the subject is moving only the actual shutter speed will do anything to "stop" that motion in your image.

So all those super crisp picture that are taken of people in sports with the L IS lense are mostly due to superior ability and the L factor and have nothing to do wiht the IS factor?

I have seen alot of pictures of birds in flight and sports that were taken with the IS on and they are SUPER crisp and sharp....

It isn't IS that "stops the action". It just ain't possible. IS only corrects for camera/lens movement. It has not a clue about what the subject is doing.

The good crisp photos you speak of were probably taken by photographers who know and use good technique along with good equipment, and possibly use IS to help prevent problems with a little camera movement. It is quite likely that they were using fast lenses that allowed for higher shutter speeds.

So essentially the IS takes the shake out of the photographer (within reason) and not the subject, right?

yes. I'm sure sony has a diagram of how their incamera IS works, and that better expains it. basically theres a tiny gyro in there, and if it senses downward movement, will move the element up to compensate, except to any direction. Newer IS models ahs a Mode 2, which shuts off vertical stabilization and only wories about horizontal for panning on a tripod

That's backwards. IS Mode 2 shuts off horizontal stabilisation so that you can pan whilst leaving vertical stabilisation on.


David

Simply put, if you work by the '1/focal lengh' rule then if you were at 50mm and would normaly use 1/50th to get a relatively sharp image free frm camera shake caused by your hand-shake then IS will allow you to use 1/30th for the same sharp image.

Saying that, I know someone who showed me a 1s exposure with IS that was hand-held... and that passed in the sharpness stakes. Yes, One SECOND!!