The focus is sharper and colors just pop out.

The fast & silent USM focusing is unbelievable.

The motor is smooth, the focus is great and the clarity is up there with the best, but just not quite 20-70 or prime, again depends on what you are doing with it

Its very sharp and has a great auto focus.

The focus is fast and precise, and I honestly can't think of a thing I'd change on this lens, with the exception of maybe one stop faster (to f/2.8)

My first impression of this lens is that the focus is a bit soft, but I have been shooting indoors and may be seeing the limitation of the f4.

The super quiet and accurate focus and manual focus override were also a boon

I felt like the focus was not where it should

I found zooming in closely to subjects; focusing could be slower or just uncooperative

Silent, Focus is fast and precise

my camera focuses very quickly with this lens, and the full-time manual focus is great for those moments when the camera "guesses wrong" and focuses on, say, the post beside the bird instead of the bird itself.

Indoors with low light, I have trouble with this lens focusing and can only get away with turning up the ISO.

Image is tack sharp and focus is QUICK.

This lens will bring you such a sharper image as well as an incredibly quick focusing system

The focusing has been fast enough, and accurate enough, for the vast majority of circumstances in which I've used this lens.7

Nice and fast focus too.

Focus is relatively fast but sometimes gets confused with multiple focal points in the frame (this might be function of my camera as well, the Rebel T3i).

This lens has much of what you'd expect from "L" glass - fast and accurate focusing, solid construction, weather sealing, and it comes with a hood and bag

Sharp crisp pictures, fast focus and solid build.

It has an ultrasonic motor drive (USM) for fast focusing, image stabilization (IS), and a very versatile focal range that covers wide angle to mid-telephoto on a Canon 5D and respectable 38mm to 168mm (1.6*24 ~= 38, 1.6*105 = 168) focal lengths on cameras with crop sensors, like the Canon 7D, the Canon Rebel series, and cameras with APS-C sensors (1.6x

The only thing that would make this lens better is if it came in an f/2.8 version (and still retained sharp focus at its maximum aperture).

The focusing is pretty fast and accurate on my 70D.

Incredibly fast focus

Love it, great focus and quality.

range!The build quality and auto focusing are superb

I have taken nearly 20,000 images in these past 6 months, and continue to be astonished at the super sharp images, very low chromatic aberration, and fast focus lock

It's very well made, a little lighter in weight compared to the 24-70, sharp, and fast focusing

Fast auto-focus

Color, contrast, sharpness (even wide open at f/4), ultrafast & silent focus and built quality are excellent qualities

The focus is quiet and fast; the sharpness, while not perfect, is great; and IS (image stabilization) is very handy

I was extremely disappointed in this lens because of the extremely slow focus

The 70-200 is far superior in the overlapping region, and offers more reach, the 17-40 offers far wider range and much better contrast and even better resolution in 24-40 range (yes, I was lucky to get a great copy of this lens), and 50 f/1.4 is superior at 50 mm in terms of resolution (when stopped down to f/2.8 -f/4), bokeh, lightness and compactness

At the "normal" range of 50mm, my humble Canon 50mm f/1.4 has considerably better color and contrast, not to mention better low-light capability

The f/4 is plenty fast for almost all your needs and the IS provides a leeway that not even f/2.8 (non-IS) can give you

Very nice focal range for general purpose with constant F/4 aperture - Reasonable wide to short tele

I am already eyeing 17-40 f/4 and even worse, 14mm L

I have a f/1.4 fixed lens that works much better in low light.

If the f-stop changes between shortest and longest zoom settings, then the video will get brighter or darker as your zoom or follow focus your subject

Upgraded from the Canon EF-S 18-135mm and the difference was incredible

(Note: it has an EF-S, not EF mount, so it's not compatible with the