Canon EF 24 mm F/2.8 Lens

The Canon 24mm f/2.8 is Canon's entry level 24mm full frame prime lens. On a cropped frame this gives us around 38mm, and on a full frame it puts us smack bang in the middle of most wide angle zoom ranges (full frame 24mm is around the same as 15mm on a cropped frame). This makes it an excellent choice for a budget wide angle lens, perhaps for a photographer who doesn't shoot landscapes as a priority, but wants some wide angle capabilities.
When I say entry level, I mean it. The lens is very rudimentary. It has quite a plastic feel to it and a very cheap and cheerful construction. On the plus side, this keeps the weight down, and it is absolutely tiny (not quite as small as the Voigtlander 40mm, but lighter). The lens has no weather sealing, no ultrasonic motor and no manual focus override. What is does have, is some pretty high quality glass.
The center image quality is very good from wide open and becomes fantastically good when stopped down a little. Edge sharpness lags behinds around 2 stops but gets pretty good around f/5.6. Full frame (extreme) corners are a little disappointing and don't really reach acceptable levels until f/8, between f/2.8 and f/4, corners are plain awful. This shouldn't bother landscapes photographers who will want the smallest apertures possible, but for other uses these limitations will need to be taken into consideration.
Chromatic aberration can be a bit of a problem, especially if using wider apertures. Once the CA is smeared into the blurred corners, there's no getting rid of it (this is the same problem I experienced with the 17-40 f/4.0L). As long as the worst areas are sharp, CA can be removed with a simple Red/Cyan (-18) adjustment in RAW. I am surprised that at the time of review, there is no Adobe lens profile for this lens, being a still-in-production Canon lens. However, the lens design is almost as old as me (1988), and will probably be replaced soon.
A complaint I heard repeated a lot online while I did my research prior to buying the lens, concerned the autofocus. Many people disliked the noisiness of it, being non-USM. My take on this is; yes it is noisy, but it is actually very quick and precise. A lot of the time, it is so quick that I don't realise it has worked! Chances are, you will almost always be using the lens focussed between 10m - infinity. Within this range, the addition of USM would have been a waste of space, you can't hear it! If you focus down to 30cm, then to infinity, yes it whines at you, but it doesn't take long. Anyway, at 24mm, it's unlikely you are going to be disturbing any animals with your noise. To be honest, I'd rather have the price break than the USM.
Manual focus, on the other hand, is pretty rubbish, without manual override, it would have been nice to have some damping on the focus ring (the focus ring is completely disconnected and loose when AF is engaged). There is a fair bit of play in the ring, but it is still perfectly useable.
The lens scores high points for practicality, the front element does not rotate or extend during focusing, and the size of the whole construction means it can be taken anywhere. It would have been nice to get a hood with the lens, but leaving it out seems to be Canon's policy with non-L lenses.
In conclusion, I would recommend this lens as a budget landscape lens for a full frame user, so long as large apertures are avoided. For a cropped frame user, it would make an excellent value wide/normal lens.

This lens was bought for my ex 5D which needed something fast, wide and small for travel and day to day use. After researching options I found the classic 24mm prime, which seems to have been forgotten about in these days of 1.6x crop bodies. Works great on FF and does well as a nice walkaround on a crop. Very low distortion and bright/vibrant colours. Can't fault it apart from the typical Canon plastic body found on all their mid market primes. AF is pretty fast but just a tad buzzy - no problems at all with that though.

I decided to buy this lense as I was unhappy with the sharpness of the kit lense (18-55mm IS). I read a lot about this lense on various sites and there are mixed reactions to it. One site talked a lot about Vignetting (it is there) while other praised it for being a cheap and lightweight prime.

This lense is really good on my 450D with the vignetting issues resolved in Canon DPP as I always shoot RAW.

In the end, it is a balance between how much money someone wants to spend on lense equipment. If Money was no object, the Canon 24mm TS-E lense would be the ultimate in sharpness and image quality. It is also 4.5 times more the cost of this one. The issue here is that you dont get 4.5 times more image quality given the curve of diminishing returns, and further to that you will also need a dang good sensor (Canon 5D MKII or Canon 1Ds MKIII) to be able to capture that image quality.

Decent if not stellar build quality. Optically pretty good, focusing slightly noisier than USM lenses but perfectly OK. No FTM. Hood difficult to find. Nice fast maximum aperture though!

Pin sharp, great focusing and excellent value for money. This lens is very popular and well loved and deservedly so. check out the flicr group named after the lens.