Image Stabilization Question

[redsnapper]

Hi All,

I'm a newcomer to IS lenses, and have just taken receipt of a new Canon 40D with 28-135mm IS USM lens.

It's difficult to tell whether the IS is working. I've read that it makes up to three stops' difference, but mine seems to be making little or no difference at all. If I have the camera on, say, Tv mode, should the shutter speed jump up when the IS is put on? Or does the IS effect not show on the exposure info? If not, how are you meant to know what speeds/apertures you can get away with?

Apologies for the novice question. Explanations greatly appreciated.

[flake]

You shouldn't notice any physical difference when you have the IS on nor will it change any of the values displayed on the LCD.
The rule of thumb for camera shake is 1 over the focal length so if you have 100mm you need roughly 1/100sec shutter speed working that backwards by three stops (and 1/100th is a half stop value) you have a shutter speed of around 1/12 sec.
Thats the easy bit, the rest of it depends on things like how steadily you can hold the camera, you might get more or less in the way of shutter speed, before camera shake is an issue, and then factors such as the wind and peoples movement can all conspire to reduce that advantage.

I think the best advice would be to look for a small table of shutter speeds, (stops and half stops), look at what focal length you have, and what the camera is telling you it wants for a shutter speed, then working back by three stops check the speed is faster than the rule of thumb. The rest is down to experimentation and chancing your arm I'm afraid because it's going to be different for everyone, even the way you stand can affect it.

[chris-p]

I don't know how Canon's IS works but it can't be that different from Nikons and I can see it working through the viewfinder.

It's more obvious at longer focal lengths, of course, but when I half press the shutter release I can see the image stop moving as much. Do you not get that on Canons?!

Flake, you'll know the answer to this...

[Forseti]

Originally Posted by chris-p

I don't know how Canon's IS works but it can't be that different from Nikons and I can see it working through the viewfinder.

It's more obvious at longer focal lengths, of course, but when I half press the shutter release I can see the image stop moving as much. Do you not get that on Canons?!

...

Yes, press the shutter half way and the image freezes. However, we're talking about normal camera shake here, not someone suffering waving their arms about.

To the OP - I can't swear to it without looking it up for myself but I find that an increase of 3 stops with this particular lens to be somewhat optimistic. Perhaps you could enlighten us as to where you gathered or read this information. I owned this particular lens a while back now and if memory serves me correctly it is fitted with the first generation of IS. Also, to check it's working - hold the camera up to your ear, half press the shutter and you should hear the IS kick in, it's a kind of whirring sound.