On my Canon Lens there is a button for Stabilizer Mode 1 or 2....what is the difference and when to use either one.
To expand on the above and correct a couple things...
Mode 1 is STANDARD two-axis stabilization (both vertical and horizontal
) and is what you will want to use most of the time.
Mode 2 is for PANNING... providing only single-axis stabilization (on the vertical
axis only, regardless of lens/camera orientation). Mode 2 turns off horizontal
stabilization so it doesn't work to counteract the deliberate background blur being done with the panning motion and a slower shutter speed (i.e. "dragging the shutter").
Here's a panning example (EOS 50D at 1/60 shutter speed, ISO 100... 70-200/2.8 IS lens at 100mm and f16)....
And for comparison, here's an action-freezing example (EOS 50D at 1/640 shutter speed, ISO 200... 300/4 IS lens at f5.6)...
So, basically there are two ways to depict action in still photos and/or help isolate a subject from a busy background. Panning will usually make for fewer "keepers"... some percentage of shots simply won't work out, but IMO often makes for a more "active" looking image. The partial blur effects produced by panning also work to separate a subject from a background (or foreground), much like controlled depth of field effects can, when using a large aperture with a longer focal length.
Canon now is also putting "Mode 3" on some lenses (EF 100-400mm IS USM "II", for example). This is INSTANT stabilization. It provides two-axis, but only during the actual exposure. IS doesn't run constantly, the way it does in Modes 1 and 2. Frankly, I'm not sure when or where I might use this. I like
that standard or panning IS also stabilizes the image in the viewfinder, much the way that stabilization on binoculars is helpful, especially when tracking distant, moving subjects with a long focal length lens. Also, after 15 years using Canon IS lenses, I think it often helps autofocus a little by stabilizing the subject the AF sensor(s) is trying to focus upon and track. (Note: Nikon users feel the opposite, that their VR actually slows AF). But, even if I never use Mode 3, at the very least it suggests the lens' IS system is extremely fast, in order to be able to do its job during the fraction of a second of an exposure!