I bought this lens after contemplating buying the new 16-35 2.8. I had the money to buy the more expensive lens but I didn't and here is why. I was told by an aquaintance who test for Canon that the 17-40 f 4.0 is over all sharper and has less distortion than the new 16-35 f 2.8 (as of Aug 15 2007). I have heard this from other photographers as well. Also although it isn't an f 2.8 as like the 16-35 it does have a bit more range and I have found the focusing is pretty fast regardless. I think it is the best $700 I ever spent on a piece of camera equipment.

I finally got this super fast 35mm lens after years on the original EF (nifty) 50mm f1.8 and I'm blown away. The colors seem to have a cooler tone than with my 70-200 f4L IS or 16-35 f4L IS (possibly that Blue Refractive optical element) but this is preferable to me. I often regret stopping this lens down in any other setting besides direct sunlight because it is super sharp corner to corner at f1.4 and everything is in focus when focused near infinity. The closer you get to your subject at f1.4, the more your photo becomes an elegant work of art with bokeh that just melts away but yields a nice wide angle view of the subjects environment. Fast enough to catch that split second smile on your significant other's face and give them the separation from the background that just makes them pop. People become electrifying when captured with this lens. Every photo makes me smile with joy and love. If you are a photographer and you love capturing beauty in a setting, you need this lens. Don't fool yourself by saying you can't afford it, sell all your slow f4 zooms and maybe a toe to capture the world through 35mm.

These are the ticket if you need this type of adapter. Strong and secure. The price is right, as well.

Image quality is decent, when using it with 70-200 f2.8.If you don’t want to invest on a tele prime, this is a cost-effective way to extend the range of telezoom lens.

I spent a lot of time hemming and hawing between the 50mm f/1.8 and the f/1.4, but $125 you can't go wrong with the f/1.8.I researched both lenses and compared sharpness, vignetting, and other aspects of image quality on the-digital-photo [dot] com - it's a great website providing objective evidence of how canon lenses (and cameras) perform on standard image quality tests. As an engineer, I like that stuff.I've taken about 300 pictures of the wife, kid, and dog -- not the most rigorous testing by any means -- but I bought this lens for that purpose, and in that application I want the subject in (more or less) the middle to be sharp, and everything else to be totally out of focus. In practice, my better shots are at f/2.0 to f/2.8 because the depth of field is razor thin at f/1.8. If I was very concerned about things in the corners of the frame being tack sharp (e.g., landscape/cityscape), I would use a smaller aperture or a different lens. This will clearly do well in low light, but so does my 24-105 f/4.0 L IS - it all depends on what I'm pointed at.Maybe taking the same picture with the f/1.4 or f/1.2 would show me the inadequacies of this lens, but frankly, for $125 it takes nice photos with beautiful bokeh and solid mid-frame sharpness at a wide open aperture.Likes: Inexpensive. Fast. Metal mounting is a nice addition from previous models. Aperture blades are round, and there are 7 (vs 5 in previous version), so out of focus point light sources don't appear pentagonal. Stepper motor provides adequate focus speed - not bad, but not great.Complaints: Cheap plastic construction on the rest of the lens. AF is a little noisy and not as swift as other Canon lenses.

F1.8 is superb for low light and moving subjects. Fast Auto-Focus and Image Stabilizer makes this a must have for anyone looking for a budget prime RF lens.

What can I say that has not already been said???? I decided to fork out the cash for this lens, instead of going with the f4 IS version.... I am soooo glad that I got this lens! it is amazingly sharp, versital, and fun! Combine this with the 24-70 f2.8 L and you have a combo that cannot be beat, unless you want to pack around a ton of primes! Sometimes I do this.... but these two bits of glass work great together..... sharp sharp sharp

I debated for quite a while between this lens and the 17-55 f/2.8 EF-S IS. I'm still drooling over that lens, but what it came down to in the end was my plan to upgrade to the 5D when, and if the Mark II is released. Of course, the other lens that could have made the decision even more difficult is the 16-35 f/2.8L, but it was way out of my price range.I'm happy with my choice. The lens is well built and sharp. If I have any complaints it would be CA. This lens does tend to show a bit of color fringing, but nothing and extra five seconds in raw processing can't fix. So I guess that point is moot.Overall, this is a good lens. Well worth the money. Especially at this price.