300 F4L IS...IS effective shutter speeds??

[Gonebrdn]

OK, I've made the jump from Nikon film to Canon digital.....a fresh fish.

On receiving my 300 F4L IS (a few quick bird shots confirm this is a fine lens) I made the mistake of reading the manual that comes with the lens. It informs me (pg. 22) that IS is "effective" sans TC at "1/30-1/125 sec". Hmmmmmmmmm......

Lemme get this straight: if I'm hand-holding a wing shot on an albatross going by the ship IS is ineffective above 1/125 sec? Somehow I didn't expect this. I guess I can assume that it has to do with the internal mechanism itself, it's lag time, being cancelled by faster shutter speeds?

Can anyone help me out here--either share your experience with this lens re: IS, or give me a Reader's Digest explanation of the reason for the narrow range of effectiveness?

Many thanks.

[dhbailey]

I think it is less a matter of it being ineffective, more that at speeds above 1/125, you won't need to use it. Even in the digital world, the old rule-of-thumb, that shutter-speed should be at least 1/focal-length holds true for good handheld shots. IS allows you to shoot handheld at much lower speeds, and at anything equal to or faster than 1/focal-length, IS isn't necessary.

[Jon]

At higher shutter speeds, the IS effect won't be as noticeable because you're not as shaky, so it has less to work with. If you're allowing it to warm up properly, it should be able to keep pace with micro-trembles at any shutter speed.

But 1/30 to 1/125 is for the "normal" user, not an absolute. If you need to hand-hold a 300 mm lens at 1/1500 to get a steady picture without IS, you should see the effect beyond 1/125, maybe to 1/500 or beyond. If you can hand-hold it down to 1/125 and get good results, IS may push you down to 1/8, but you wouldn't notice the difference between IS and non-IS at 1/60.

At the other extreme, if the camera's steady, the IS will try to correct for that (notice the caution about turning it off when on a tripod?) and make the picture worse.

[Gonebrdn]

[QUOTE=Jon]At higher shutter speeds, the IS effect won't be as noticeable because you're not as shaky, so it has less to work with. If you're allowing it to warm up properly, it should be able to keep pace with micro-trembles at any shutter speed.

Thank you for this comment, this is more in line with what I expected when I purchased the lens. I suspect that the comment in the manual is an exercise in managing customer expectations.

You note that I should "allow it to warm up". The manual notes an approximate one second lag from depressing the shutter button half-way until the IS ready to go--is this what you meant, or were you implying something else?

Thanks for your response(s)!

[Jon]

Yes, I was referring to the 1-2 seconds for the gyros to get up to speed and to work out how shaky you are. A little longer won't hurt, except possibly in battery life.