deletemenow

Looking at my last post, I didnt' mean to imply my experience would duplicate on the 100-400 L IS. That lens mey behave differently.

It's easy to test. Take a series of longer exposure (1/2 - 1 sec) shots zoomed in on some detail, with and without IS, and compare results.

Also use a shutter remote to minimize movement.

I replaced my 70-200 IS assuming that the "special mode" Canon refers to was somehow broken.

The new lens behaves exactly the same way, so so much for Canon's explanation.

So from now on I will use IS on tripod only when I'd like a random bit of blur in the shot :)

Another thread on this subject: http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00EPRj .

Although Canon says both in manuals and at http://www.cps.canon-europe.com/kb/detail.jsp?faqId=1130 , that IS can be left ON on a tripod, and in fact should even improve results, my experience with two 70-200 2.8 IS's is that IS will cause blur when on a stable tripod.

The movement that IS causes on a tripod is plainly visible through the viewfinder, and I think your tripod would have to be very rickety or it would have to be quite windy to warrant using IS on it.

I tried the experiment as well and also got noise. But this was only due to PS_CS2's RAW import auto-exposure and brightness controls trying to bring some detail out a of such a dark image.

It seems reasonable to me that the sensor would not generate actual zeros under blackout conditions, since it would cause faint to be too close to the sensor's lower threshold of sensitivity.

Any transducer has a non-zero noise floor.

I think the camera's default conversion from camera RAW to JPEG (12 > 8 bit) compresses the blacks, so you see them as black in JPEG.

As I understand, this is one of the benefits of RAW, namely the ability to reveal detail hidden in shadows.

If you have astigmatism I assume a built-in diopter adjustment can't solve it, right? Can you get add-on that matches your glasses prescription exactly?

How about a piece of black felt/cloth affixed to the rubber:

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I just bought a 70-200 IS today and noticed the tripod issue right away - hence a search that lead me to this thread.

The thing that worried me is that on the tripod, with IS on, it never seemed to settle rock solid. So my suspicion was that it would drift a tad while the shutter was open as well.

After reading the Canon FAQ above the explanation seemed reasonable so I decided to test it.

I shot 4 series of 5 shots each with IS on and off. Two series were at a shutter speed of 10 seconds and two were at 20 seconds. Of each of those, one series was at 200mm and the other was at 400mm (2x extender). Examining each one zoomed in, virtually all the IS shots were slightly less sharp than the non-IS shots. The difference was subtle but consistent.

With IS on, the image in my viewfinder shifts to the left when the shutter button is pressed halfway, not vertically up like the Canon FAQ says. Regardless of the direction of shift, when tripod-mounted, I certainly prefer the image not to shift at all - especially for no benefit that I can detect.

I don't think I get any of these issues with my 17-85 IS, and in handheld tests, its IS seems to be a bit more effective than the one on my 70-200. Of course the latter is longer and heavier, so there could be other factors involved.

Bottom line, I'll take take the advice of my manual, which says turn IS off when on the tripod. But I'm frustrated that after spending $1800 for the lens that I find this functional and documentation issue. It just makes me wonder if something's wrong or if I got what I paid for.