Canon EF 100-400mm f/4.5-5.6 L IS USM Reviews

Although this is a somewhat slow lens I have been very pleased with the optical quality. Most of the wildlife photography I do requires hand holding the camera. The IS works great at 2 stops and can be pushed a little more (2/3 stop for me) with careful technique.

The push-pull zoom is odd and I am somewhat concerned about sucking dust into the lens/camera but only time will tell if that is a reality.

No dust-sucking problem. Rather big, but ok, it's a 400. IS does a good job, image quality is very good, but not as outstanding as other L lenses. Consider buying the EF 70-200mm 2.8 L IS USM instead and using a converter if long end is really necessary.

A very nice lens for wildlife photography. The IS works really well and compensates for the relatively slow maximum aperture (f/5.6).
Excellent build quality and, though it takes a little bit of time to get used to, the push-pull zooming is brilliant.
Good sharpness and definition but not the sharpest lens I've ever used.
It's quite light for a 400mm zoom and looks cool too!

Primary use is wildlife--almost exclusively hand-held shots. I sell my photos in a local gallery.

Pros: IS gets me 2-3 extra stops. Lens quality is very good overall. This lens produces a pleasing rendition of out-of-focus background clutter.

Cons: Mechanical--This lens sucks a LOT of dust onto my sensor. The slide ring friction adjustment is terrible. Unless you set it all the way loose, it grabs unevenly through the slide range. Ocassionally it locks shut and won't release. This complaint is echoed on the Web, and I concur.
Optically--this lens is quite soft at 400. Shots at 300 blown up are almost as good. My Sigma 100-300 matches this lens quality, and I like the zoom lock better.

It may be worth noting that my research before purchase indicated there may be considerable variance in sharpness between individual copies of this lens, per user reviews.