Quick question about shutter speed @ 200mm w/ IS

What is the lowest handheld shutter speed you can use at 200mm using IS?

I'm considering the 70-200L f/2.8 IS.

What's the lowest shutter speed you can handhold using the 70-200L f/4 IS? Is it one or two stops lower than the 2.8's IS?

Should be, given Canon's description of the f/4 IS, about the same light level, maybe a stop slower shutter speed than the f/2.8 IS. That's only if you give the camera a longish time to spin up the IS mechanism.

1/25 with good result, 1/15 - 1/20 with luck

luant16 wrote in post #2341535
1/25 with good result, 1/15 - 1/20 with luck

Are these speeds at 200mm?

I took a shot last year with my 20D, fitted with my 70-200 f/2.8 IS screwed to a Canon 1.4x extender, for a real focal length of 280mm (equivalent to a 448mm lens on a 35mm film camera). It was such a fast shot that I failed to look at the shutter speed - it was 1/15 second. The shot came out a little blurred due to handheld instability, but was quite acceptable under the circumstances. The shot is attached to this thread if you'd like to see it.

1/60 th consistantly. 1/30th often

Tapeman wrote in post #2343474
1/60 th consistantly. 1/30th often

These seem reasonable - with my 24/105 racked out, I can get 1/30th consistently, 1/15th often. And 1/10th occasionally.

The lowest hand hold shutter speed depends on how sharp a picture you need, your ability to hold the camera steady, what percentage of acceptable pictures you want and whether the subject moves. There is no answer that is meaningful for all situations and the best you can hope for is a rule of thumb or what other people find acceptable for their ability and standards.

The only important factor is that you can shoot at get the shutter speed with an f/2.8 lens that you do with an f/4 lens in low light situations. As long as the depth of field is sufficient, that gives more choice over ISO setting and the ability to shoot moving subjects. If we have to shoot wide open, we don't have control over the lighting so we want the lens that is most capable in the worst conditions we are likely to encounter.

In my mind the choice between the f/4 and f/2.8 versions of the 70-200 is a choice between the lower cost and less bulk and weight of the f/4 vs. the better low light capabilityies of the f/2.8 and the 77 mm filters that are interchangeable with a great number of other L and EF-S lenses.