I bought this to replace another lens that failed several years ago, so I have had plenty of experience with it shooting various wildlife, primarily birds for large prints, typically up to 36 inches on a side, using a Canon 40D, then a 60D.This lens is capable of extremely high IQ images.

Consistent Output; Durable; Easily Interchangeable; Fast / accurate auto-focus; Lightweight

Maybe Soft Wfilters; Maybe Soft W Filters

A good entry level bird/wildlife lens. Takes a bit of practice to get sharp shots handheld.

Well made; Sharp; Not too heavy for a 400, but not exactly light either; Good value; Works pretty well with the 1.4x extender; Fast autofocus

It could really use IS

I purchased this lens for bird photography and am very happy with it so far. It is lighter than the 100-400mm Canon and have found that all my pictures are at 400mm anyhow. The lack of IS might be a problem for some especially in dusk/dawn situations when you need to slow the shutter down.

Durable; Fast / accurate auto-focus; Lightweight; Rugged; Strong Construction

Poor in Low Light

Brilliant optics, tack sharp wide open with aps-c , razor sharp on FF !! Wish canon had added IS to it to compensate for the slow aperture.

A very fast focusing lens on canon. MTF chart of the lens says all about the picture quality

I bought this for a trip to BC/Alaska, and it's my first Canon L lens. It may have cost me an arm and a leg, but it is solidly built and focuses very fast. I bought a monopod at the same time but it could really do with a pistol grip screwed into the lens's tripod bush when you're shooting hand-held...

I'm using this lens and an EOS 700D on an internet controlled astrograph. The build and the image quality over the entire field are both absolutely superb. Ultimate picture quality appears to be limited by the camera sensor, rather than the lens. Just amazing. Next, a x2 extender.

how sharp do you want,i use hand held most times and get lots of keepers ,use a 1D MK111 no problems with this kit I use for Birds and surf sports, as good as the big bucks

Fast auto-focus; Superior build quality; Super-sharp images

Just purchased this lens and have spent time out birding. I've used it with and without an EF Extender 1.4x, and both hand-held and on a solid tripod. I'm very pleased: without the extender you can (with large hands and steady arms) shoot hand-held for quite a while.

This is the ultimate best birding lens for hobbyist photographers. I agree, in theory the EF 300mm f/4L IS + 1.4x extender should be better but actually it isn't as per users' opinions. I have owned this lens for 17 months and shot thousands of images with it mounted on my EOS 450D and EOS 50D.

a; Lightweight b; Affordable c; Sharp d; Fast autofocus

a; Lack of weather sealing