This lens is sharp don’t get me wrong. I have taken some amazing quality pictures even at high apertures. The thing is, it gets a bit soft wide open. The focused area is sharp, but not as sharp as I would like it to me. Also, the DOF is very shallow, and the quality softens very fast once out of the focused area. If you are trying to take a picture of two people and they are not exactly at the same distance from the camera, forget about it. One person will come out as background blur. That means that in low light situations you have to use a much higher f number, which defeats the purpose of having an f/1.4
Compared to the 35mm f/1.4 you have to know that this lens excels at a few things. For example, the background blur is amazing on the 24mm. Very creamy and pleasant. The 35mm produces a much choppier blur.
This lens is wide, and that can be seen on a full frame sensor. I shoot with a 5D, and close to the edges it distorts the images. Make sure you do not have your main object close to the edges, or it will get distorted. However, if you have a crop factor camera (30D, Rebel, 1D, etc.) you might not even notice this effect. I doubt the lens barrels than, since the crop comes from the middle, avoiding the problem spots. Never-the-less, the distortion gets annoying when trying to shoot people. For other objects it is not as noticeable. In conclusion, it is a 24mm, and even the renowned 24-70mm barrels, so what can you do?
Colors are beautiful, saturation is rich. A true “L” lens. Contrast can get a little soft when wide open. It can produce a sort of dreamy effect when used at apertures under f/2 - from a softer sharpness to a more flat contrast. Not a bad thing, but you have to be aware of what you want from your shots.
Overall, I would say this lens deserves the “L” designation. Very dependable, producing quality material. I would recommend it, but be aware of its shortcomings, and make sure it fits your shooting needs. To be frank, this lens is not my favorite, and does not see a ton of use. My most used lens is the 70-200, but than again you can’t compare the two. However, for a wide lens I don’t see a better choice than this. The 14mm is not even in the same league, and the 35mm is not any better plus it is not as wide.
A very clear choice here!