Canon EF 17-40mm f/4L USM Ultra Wide Angle Zoom Lens for SLR Cameras

If you're shooting an APS-C Canon and you've decided that you only want EF full-frame lenses for future use on a full frame camera, the 17-40 is a must-have. The focal range on the cropped sensor is 27 to 64mm which covers a large range for the majority of shots most people are likely to take. I've found this lens is perfect for social gatherings and essential for group shots. The size and weight is perfect on the 7D, making this my favorite lens for handling (compared to the 24-70 f2.8L and the 70-200 f4L). The build quality is superb. The focus and zoom rings couldn't be smoother and AF is fast. While this is a sealed lens, I hear that it's not fully sealed until a filter is fitted. With one in place, the zoom extension is completely internal, so there's no change in length when zooming from wide to the long end.This lens is a fixed f4. If you buy the lens with the understanding it is not an f2.8 and will not get you the lower ISO and/or faster shutter speed of an f2.8, the lens does very well in most shooting situations. On the 7D it's even better with the excellent high-ISO performance of that camera (I can shoot at ISO 3200 to 5000 without much concern). While it is reasonably sharp at f4 across the focal range, it is not as sharp as when stopped down to f5.6. Also, boarder sharpness falls-off a bit wide open and close to 40mm. However, these are not big issues. Contrast and color with this lens is excellent. My only caution from experience is to be careful when adjusting the point-of-focus to depth-of-field balance with the micro AF adjust on the camera (if you have that feature). What may appear to be a correct adjustment with a focus scale sheet that uses the center of the field, may end up causing excessive edge softness of your images due to the edge of the frame starting to fall out of the depth of field. I believe this may be due to the field curvature characteristic of a wide angle lens where the focal plane is not equidistant from the camera lens but slightly curved. I spent some time setting the correct AF micro adjustment by photographing a large bulletin board with very small lettering and symbols across both dimensions while making sure the camera was pointed square to the center so that all corners were equal distance from the camera. Once you have this dialed-in, you can test the center-to-corner sharpness of your lens at different focal lengths and apertures and determine whether you may have any sharpness issues with your copy. Initially I thought I had a bad lens copy that was soft and de-centered, but after getting this procedure right, the lens proved to be sharp.While there are other excellent options such as the Canon 17-55 EF-S f2.8 lens, this one is full-frame compatible, it's weather sealed, it has superior build quality, it's an L lens with that unmistakable red ring at the end, and it's the next greatest lens bargain second to the 70-200 f4L. While the hood may look odd, remember that it was intended for a full-frame camera where this lens would be a true 17-40mm - making a shallow hood necessary.

I purchased this lens to accompany my new 50D. The first thing I will note is the amazing improvement upon image quality when moving from the 18-55mm IS kit lens to this one. As there is quite a bit of difference in build quality as well as price range, that should come as no surprise.If you are shooting with a crop body camera, Rebel/XXXD or xxD body. The extra range on the short end of this lens becomes really important when shooting group pictures, landscapes, or your shooting space is really tight. The difference seen between having 17mm at the short end and 24/28mm is really REALLY noticable and allows you to get some landscape and close quarter pictures, you might not have been able to take.As far as build quality goes, the lens is VERY solid. Metal construction with LD glass elements and very smooth focus USM motor and like butter zoom ring, it all just feels wonderful to use. You will definitely notice a difference if you try to use a lower quality lens.Optical quality is amazing. As the sensor on the 50D is very dense, it becomes easy to see the flaws in lower quality glass. This is not the case with the 17-40L. Though I would have like to be able to get the extra f stop that comes with the 16-35mm 2.8L , the decrease in weight and the HUGE decrease in price makes the 17-40L a better deal for me. After all, the bokeh becomes the only reason that the fstop is so important(i wouldn't discredit this because smooth bokeh makes portaits great) , as the difference between f4 and f2.8 is going from about ISO 200 to ISO 400, and with the dramatic increases in high ISO perfomance, it is likely you will not greatly notice the difference. If lighting is THAT bad, you should really be using a fast prime, such as the 50mm 1.4 or an external flash.The EF mount makes it easy for one to make a switch to full frame camera in the future and will leave you with a very useful ULTRA-WIDE lens on FF cameras.Overall, I am very pleased with my purchase, and if given the opportunity to purchase again, I would happily do so. In the future I plan on paring this lens with a 70-200 f4 L which I understand is one of the best priced and best value canon lenses made.