100-400 IS L series lens

I have 2 questions I guess.

I was told that a IS lens could not be used on a tripod. Reason being the IS seeks to stabalize movement. If there is no movement on a tripod, the IS gets confused(?) and a blurry image is created. Sounds crazy to me. So, can one use a IS on a tripod?

The other question is would you recommend the 100-400 IS over a 400mm fixed focus and why. I currently own a 300mm 4.0L and love it. I back pack often and know that the weight of a 400mm 2.8l is something to consider in comparison to the 100-400mm L.

Ok, one more question, is the glass quality as good as the 400mm? Thanks

Yes, you can use an IS lens on a tripod. Just turn off the IS feature

when you do so.

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Since you already own a 300/4, I'd suggest buying a Canon 1.4x to get

your 400/5.6 lens. Quality is excellent, and the extender, while not

cheap, if far cheaper than buying the 100-400 IS or a fixed 400/5.6

(much less a 400/2.8!).

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UNLESS you really desire IS functionality in the 100-400 range, in

which case the zoom's a sensible purchase. Even in this case, I'd

recommend you consider selling the 300/4 and replacing it with the

300/4 IS (and extender) since it appears you are primarily interested

in the longer lengths. That gives you prime lens sharpness at 300/4,

excellent results at 400/5.6, and of course IS functionality.

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Again, though, let me emphasize that there's no reason to buy an IS

lens if you shoot off of a tripod most of the time and if doing so

fits your shooting style.

I have been using a 300mm L IS for about a year now on and off the tripod.

Regarding the IS function on the tripod if you look carefully you will see the image

frame "wander" when IS it tries to compensate for non existant movement. Without

having got a sensible answer from Canon in Norway I deduce from this that when you

go slower than 1/15th this is going to cause problems. I haven4t done any tests though

and only use IS on the tripod if I am working fast hands on camera or if there

is a lot of wind. Otherwise I stick to "conventional" methods......Mirror lock with the

2 sec timer is my favorite.