This is a cheap lens - old design, very plastic - that can prove terribly useful for those on a budget who want a wider perspective, especially on 1.6x crop factor dSLRs.

I learned about "cheap" with this lens - broke the focus ring the day after delivery. But I blame myself too, and the replacement's given me no trouble, though I think my first one was a bit sharper than the second.

By many standards, this lens will match or exceed zoom lens of comparable price (as a prime lens should). Autofocus is a little buzzy, but the main time you'll notice is when it loses its bearing and suddenly lurches way off target. Mostly, focuses quickly enough and well. Some chromatic aberration in worst-case scenarios, but nothing awful or unexpected. Vignetting, even on a 1.6x crop, can be noticeable, mainly in sky shots, but gradual rather than sudden. (Might be unacceptably worse on a full-frame camera.) Undue distortion seems minimal - haven't really checked but also haven't really noticed, if you see what I mean. Flare seems average, perhaps better than one would expect from such wide glass. Bokeh is nonchalant, not dreamy but never intrusive.

But at the price, the positives make up for the negative and "average" tendencies. It's vibrantly colorful and contrasty almost to a fault. Hard light is a little more challenging with this lens, a little more tricky to balance exposure between highlights and shadows. It's softish wide-open, but very unobjectionably - have yet to regret shooting at f/2.8. My main lens is a 50mm f/1.4, and switching back and forth on the same aperture setting is perfectly functional in practice. Lose a little crisp for taking in four times as much space, and that's a trade-off I can run with. (Their filter threads match too.) At f/4 and higher, I get "plenty sharp," though I've never seen "unreal sharp" from this glass (as I have from the 50mm).

"Crop factor" over-simplifies the effect of mounting a wide-angle lens on a 1.6x camera. Yes, the field of view will match 40mm on a full-frame, but the perspective will not, because you'll be closer to your subjects. Shooting live subjects (like bands, models, or street life) will require a learning curve, so beware mission critical work before you've broken yourself in so you can anticipate its exagerations.

That said, I bought this lens primarily for "head-to-toe" model shooting in my modest studio, and it's been a real asset. Interestingly, it tends toward a very useful "slimming effect" that makes hippy girls look more slender and shorter girls more ambiguous in height (at least at the "head-to-toe" distance from them). Disconcerting at first but terribly useful once you've gotten the hang of it. (Beware chicken legs or the reverse from dramatic perspectives.)

I read every review I could find before purchase, and this lens seemed to be a magic middle between the higher cost clarity of the 20mm and the cheaper lesser sharpness of the 28mm. Near as I can tell, I nailed it. This is not a spectacular lens, but a very very functional one if you need an affordable wider angle that generally won't let you down.

I bought this lens to have a fixed, light lens to use with my digital EOS 10D (due to 1.6 crop factor it has the same viewing angle than a 45 mm lens, in the "standard" range). I use it in "keep it simple" photographic sessions.

Resolution and overall image quality are quite decent; but it has one main drawback: vigneting is non-negligible at f/2.8, even inside the digital cropped frame (so I can't guess how bad could it be in a full 35 mm frame). At f/4 it becomes usable. I've done a very informal comparison with Canon EF 17-40 L and both lenses give comparable results at f/4.

Design is old, but effective; it has a depth of field scale. I'd like it to have a more silent focus engine, or a somewhat more robust build, but it does its job.

From all the reviews I read, I expected certain pros and cons from this lens. I was not disappointed.
pros: very sharp lens with very good colors
cons: vignetting at wide open, and a little too contrasty
For myself, the pros outweighed the cons for the price. It is ideal for the 1.6 multiplier cameras, where it becomes a 38mm lens.

This is not one of those glamour lenses you read about on photonet. You know, the type that causes a feeding frenzy on the forums among those who must have the Big New Thing. It doesn't have a red stripe or exotic optics. It doesn't zoom. It doesn't attract a crowd when you use it. The reviewers don't get glassy-eyed and wax poetic about it. Far from it. Usually, the less knowledgeable put it down because it's an old design that pre-dates the Ultrasonic autofocus motors Canon has been using for several years and the widest aperture is only f/2.8. Besides, it's not an L-series lens and everyone knows that's the ultimate.

Okay. If you must have the hottest new stuff and your camera gear is more for show and bragging rights, this lens ain't for you. However, if all you really want to do is take good pictures, you really should consider this lens. The autofocus is fast and accurate albeit not silent and you do have to use the slider switch to turn it off if you intend to manual focus it. It might have a bit more vignetting wide open than you like (but I've got to wonder how often the vignetting really is an issue...maybe if you shoot only photos of a clear blue sky or blank white walls...?). It is sharp, however. It is small and it is well made. The lens barrel and focus ring are plastic but the lens mount is metal, the elements are glass and the lens feels solid. If f/2.8 is good enough for an L-series zoom....

I've always found the 24mm focal length to be most useful. A 20/21mm is a little harder to handle. A 28mm often just isn't quite wide enough. When I used manual focus Nikons, I actually wore out two 24mm Nikkors due to heavy professional use. I like my 24mm lenses. I also like equipment that performs well and doesn't weigh a ton. I'm not into the glamour factor and the only thing I want to impress others is the photographs I take, not the equipment I use. If you're that kind of photographer and you use Canon EOS equipment, you'll probably find the 24/2.8 to be very useful.

An excellent lens for the price. It is sharp, with very little distortion and good colour retention. Fast and easy to use, with good auto-focus. There may be sharper and better lenses on the market, but at a much higher price and they probably do not fit Canon Cameras

This is a very good lens, but if you don't need the 2.8 speed, for half the money, you can buy the EF-S 18-55mm f/3.5-5.6 USM that offers the same performance and has USM.

Both lenses exhibit fringing problems, and the color and contrast are not on par with the "L" class.

I own both lenses (see my lens sharpness comparison test, http://www.creative-wedding-photography.com/LensTests/default.aspx
, between the following Canon lenses: EF-S 18-55mm f/3.5-5.6 USM,
EF 24mm f/2.8, EF 50mm f/1.4 USM, EF-S 17-55mm f/2.8 IS USM, EF 24-70mm f/2.8L USM).

Pros:

Great price
Really small and light, tucks away in the corner of any camera bag
Sharp and contrasty photos that please the eye (F2.8 is about the same as my 17-40 F4 L at F4.5)
Fast auto focus that rarely hunts (slightly faster then Canon 50mm F1.8 but slower then Canon 17-40 F4 L)

Cons:

Wish it were F1.8 or faster
When the auto focus does miss the focus point it really misses
Auto focus sound doesn't last long and isn't really loud (louder then Canon 50mm F1.8) but reminds me of the sound of a drill

Purchase Reasoning:

I purchased this lens after a lot of searching on the Internet and testing at camera stores because I need a fast wider angle lens on my Rebel XTi with better optics then the kit lens and a wider field of view then my 50mm F1.8 lens have. I plan on upgrading to the Canon 6D or whatever Canon calls their newest affordable full frame EOS camera. It really sadness me that Canon has so many great telephoto and super telephoto lens and no really outstanding fast wide angle lens that everyone agrees is the best. I was not satisfied with the test results of the sharpness and contrast of the other lens I was considering the Canon EF 24-70mm f/2.8L lens which I thought should have had much better optical performance for the price. The 24-70 zoom does not even approach the optical quality of my 17-40 F4 zoom. And the Canon 24mm F1.4 seems to be about the same in sharpness at F2.8 as the 24mm F2.8 and gets really soft when opened up any wider and is far more expensive. I have tried some so off brand competitors lens and went through several bad lens with bad optics and or shoddy build which left a bad taste in my mouth. So for under $300 I bought the Canon 24mm F2.8 lens.

In Use:

I haven't yet noticed any objectionable vigneting that others have talked about maybe because I am using this lens on a cropped sensor camera (Rebel XTi). Maybe I just haven't used it in the right way although I have taken most of my shots at F2.8. Another strange occurrence is the photos look a little less sharp and contrasty at F3.2 then they do at F2.8. Once closed down to F4 the photos look better then F2.8 but still it's odd about F3.2 being worse then F2.8. Anyway the depth of field on a 24mm is so nice and I usually use this lens in low light at F2.8 so F3.2 is not an issue. If I am outside in bright light or use a flash I use my fantastic Canon 17-40 F4 L zoom lens which takes photos that seem to be the about the same sharpness and it has the convenience of being a zoom.

Back to back against the 50mm F1.8

My Canon 50mm F1.8 takes photos that are slightly more pleasing with greater contrast and sharpness then the 24mm F2.8 and as a plus I can shoot opened up all the way to F2.2. F1.8 and F2.0 are simply too soft and muddy with the 50mm. What I can't do with the 50mm F1.8 that I can do with the 24mm F2.8 is get 4 times the angle of view in a tight situation. And that's where this lens comes to the rescue. With pretty close contrast and sharpness and only a 1/2 stop loss in speed (made up for by being 24mm) I can shoot in those tight situations where I try to get everyone in the shot and can't back up anymore with the 50mm mounted on my Rebel XTi.

Conclusions, final thoughts and suggestions:

If you are on a budget and want the best optics you can get at 24mm at F2.8 for under $1,000 to cover a full framed EOS camera and widen your view on a cropped sensor camera this is your lens. I'm keeping mine for those tight situations and I'm looking forward to using this lens on a Canon 6D.

This is a nice lens, relatively small, with decent resolving power (better at close distances)and a great,IMO, focal length for an 1.6 crop.
What I didn't like was that it is relatively slow for a fixed focal lenth at 2.8, it does not have full time manual focus, my 50 1.4 seemed to resolve (this is a subjective conglomerate of resolution and contrast) better at infinity focus. As far as small primes go, this is one of the few to chose from in this range (I like pentax's selection better), it is a good performer.
Note: I find the 28mm 1.8usm edge sharpness similar.

I can't change from 4 stars but if I could I would rate it at 2 stars.

I have since traded in this soft under performing prime it's not even as good as my two zooms my Canon EF 24-70 F/2.8 L and Canon EF-S 17-55 F/2.8 IS both blow it away in sharpness and contrast.

My advice, if you ever plan on buying a good F/2.8 zoom in this range then don't buy it. If you are on a severe budget it does out perform the 18-55 kit lens that came with my Rebel XTi but that's not saying much.

Pros:

Great price
Really small and light, tucks away in the corner of any camera bag
Fast auto focus that rarely hunts (slightly faster then Canon 50mm F1.8 but slower then Canon 17-40 F4 L)

Cons:

Wish it were F1.8 or faster
Soft under performing prime not even as good as a zoom
When the auto focus does miss the focus point it really misses
Auto focus sound doesn't last long and isn't really loud (louder then Canon 50mm F1.8) but reminds me of the sound of a drill

Purchase Reasoning:

I purchased this lens after a lot of searching on the Internet and testing at camera stores because I need a fast wider angle lens on my Rebel XTi with better optics then the kit lens and a wider field of view then my 50mm F1.8 lens have. I plan on upgrading to the Canon 6D or whatever Canon calls their newest affordable full frame EOS camera. It really sadness me that Canon has so many great telephoto and super telephoto lens and no really outstanding fast wide angle lens that everyone agrees is the best. I was not satisfied with the test results of the sharpness and contrast of the other lens I was considering the Canon EF 24-70mm f/2.8L lens which I thought should have had much better optical performance for the price. The 24-70 zoom does not even approach the optical quality of my 17-40 F4 zoom. And the Canon 24mm F1.4 seems to be about the same in sharpness at F2.8 as the 24mm F2.8 and gets really soft when opened up any wider and is far more expensive. I have tried some so off brand competitors lens and went through several bad lens with bad optics and or shoddy build which left a bad taste in my mouth. So for under $300 I bought the Canon 24mm F2.8 lens.

In Use:

I haven't yet noticed any objectionable vigneting that others have talked about maybe because I am using this lens on a cropped sensor camera (Rebel XTi). Maybe I just haven't used it in the right way although I have taken most of my shots at F2.8. Another strange occurrence is the photos look a little less sharp and contrasty at F3.2 then they do at F2.8. Once closed down to F4 the photos look better then F2.8 but still it's odd about F3.2 being worse then F2.8. Anyway the depth of field on a 24mm is so nice and I usually use this lens in low light at F2.8 so F3.2 is not an issue. If I am outside in bright light or use a flash I use my fantastic Canon 17-40 F4 L zoom lens which takes photos that seem to be the about the same sharpness and it has the convenience of being a zoom.

Back to back against the 50mm F1.8

My Canon 50mm F1.8 takes photos that are slightly more pleasing with greater contrast and sharpness then the 24mm F2.8 and as a plus I can shoot opened up all the way to F2.2. F1.8 and F2.0 are simply too soft and muddy with the 50mm. What I can't do with the 50mm F1.8 that I can do with the 24mm F2.8 is get 4 times the angle of view in a tight situation. And that's where this lens comes to the rescue. With pretty close contrast and sharpness and only a 1/2 stop loss in speed (made up for by being 24mm) I can shoot in those tight situations where I try to get everyone in the shot and can't back up anymore with the 50mm mounted on my Rebel XTi.

Conclusions, final thoughts and suggestions:

If you are on a budget and want the best optics you can get at 24mm at F2.8 for under $1,000 to cover a full framed EOS camera and widen your view on a cropped sensor camera this is your lens. I'm keeping mine for those tight situations and I'm looking forward to using this lens on a Canon 6D.

Update 1-3-2008

Took this lens with me to Texas for my family Christmas get-together and it's just Ok.

I took a lot of shots inside and out with natural light and with flash assist and I'm just not that impressed. I don't think the photos are any better then the 24-70 2.8 zoom therefore I will probably sell this lens and get the zoom instead. The Canon 50mm F/1.8 at F2.5 and higher is a real looker with a wow factor resolution and colors that will take your breath away. I thought this lens could do that but I guess not.


3-28-2008 Update:

I sold this 24mm F/2.8 soft under performing prime and bought a Canon EF-S 17-55 F/2.8 which is so much sharper it's a crying shame and my Canon 24-70 F/2.8 L is sharper then this prime as well.

Lens I currently own:
Canon EF-S 17-55 F/2.8 IS Ultra sharp, great colors, great low light, poor zoom action
Canon EF-S 18-55mm f/3.5-5.6 Rebel XTi Kit lens Muddy, slow, pile of junk
Canon EF 17-40mm f/4 L Fantastic colors, pretty sharp, ultra smooth zoom action, light weight
Canon EF 24-70mm f/2.8 L Fantastic colors and contrast, sharp, zoom a little stiff at first, heavy!
Canon EF 50mm f/1.8 II Good budget portrait lens, light weight, disposable, sharp from F/2.5
Canon EF 85mm F/1.2 L II The best portrait lens for female and children clients, buttery smooth Bokeh, heavy and expensive it shares sharpness with 135mm
Canon EF 135mm F/2.0 L The best portrait lens for males and tied with Canon 85mm F 1/.2 for sharpest lens I own, buttery smooth Bokeh
Canon EF 70-200mm f/2.8 L fantastic colors, sharp for a zoom, very versatile ego boosting and attention getting and heavy!

My next lens purchase I'm saving for right now:
Canon EF 300mm F/2.8 IS L the finest lens ever made by Canon

I love, love, love this lens. It makes a great companion to my Canon EF 50mm f1.4 USM Standard & Medium Telephoto Lens for Canon SLR Cameras and has come in handy in many situations.

If you're looking for a wider Angle of View, then this lens will provide it. Whether taking landscape shots or tight interior shots, it will perform and deliver outstanding photographs.

That said, you have to be careful when purchasing filters for this lens. I purchased a Tiffen 58mm Haze-1 Filter to protect this lens and when I put it on the lens, there was a small dot about 3-5mm in diameter in the center where the filter and lens were touching each other. I ended up having to buy a more expensive, thinner glass, filter to get an acceptable fit.

Beyond that, the only other negatives for this lens are that it's more loud than my USM lens, but that's to be expected. It's also not so loud that it's distracting; it's just noticeable if you're used to USM. And the focus ring on the lens stops at either end. I prefer the way my 50mm lens handles that in you can just keep turning it and not feel like you're damaging anything internally. With this lens, I fear turning the focus ring too far.

All in all, the negatives with this lens pale in comparison to the benefits. I don't think twice about swapping the 50mm for the 24mm when the situation calls for it.