Pro: Great image quality, especially for available light portraits shot at f2.8 where you want a pleasingly blurred background. The IS is good but see note below.Con: Weight if you plan on carrying it around all day on a pro camera body.This is a great lens and if I didn't also own the 70-200mm f4.0L IS Canon lens I would have rated it 5 stars. IMHO the f4 is a better all around carry lens if you don't absolutely have to have the f2.8 aperture. The IS in the f4 is Canon's latest and is usable up to 4 stops slower shutter speed than you'd normally need at less than half the weight. The 2.8 version uses the very good, but older, 3 stop IS. On the surface you would think that the f2.8 aperture being one stop faster would place them on even ground where IS is concerned but it does not. the newer IS on the f4 version is INCREDIBLE in operation! To be fair to the 2.8 lens, given the same lighting conditions, it gives you one full shutter speed faster that may make a difference if stopping motion is needed in the shot. My best advice is to not end up with both lenses becuase it is so hard to decide which one to take along!

Perfect with an adapter for my Canon SX40. Thanks!

I got this lens a while a go...the first copy was defected but the second one was the right one....is very sharp considering that is not L series...but the focusing system is very fast...I can focus almost instantaneously...is fantastic considering the fact that is 4-5.6 lens....for everyday shots is very good...I was debating between the version of 70-300 L and this one and I'm glad that that i choose this one...considering the price.... now compared to the 70-300 Nikon version is faster and sharper without doubts,, i have Nikon and canon full frames and regarding to the 70-300 range...this canon beat the Nikon one....for sure...

nice fit and works great with both my Canon and my Nikon

Canon and Nikon need to take notice before of the word value

The walkaround lens. This very topic leads to a heated discussion among DSLR photographers.First, determine your budget, focal length, and aperture needs.If you frequently find yourself zooming out to get everything in a frame, you will want a wide angle lens such as this. If you frequently find yourself zooming in, this is not the lens for you. On a full frame body such as Canon EOS 5D, this lens becomes ULTRA wide angle. On an APS-C crop body such as Digital Rebel XTi (which I used for this review), it becomes MEDIUM wide angle. But thanks to 1.6x crop factor, this lens expands to more usable 35mm equivalent focal length of 27 to 64mm.Second, audition the lens if you can.By definition, a walkaround lens should be relatively portable. At 1.1 lbs., Canon's EF 17-40mm f/4L USM is neither super light nor neck breakingly heavy. In fact, it weighs almost the same as Digital Rebel XTi -- really nice balance. The lens feels very solid with supreme build quality that only L-series lenses offer. Although this lens is weather proof and therefore sealed against liquid and dust, I strongly recommend getting a 77mm filter to protect the front lens element. With it, this lens is made to last.In terms of looks and feel, it doesn't get much better. Its rubberized full-time inner focus manual ring USM focuses smoothly, quietly, and quickly. Since it's inner focus, the lens will not extend beyond its metal casing whether you zoom in or out. The focus window shows focusing distance from 0.28 meter (0.92 feet) to infinity. The focal length marker indicates 17, 20, 24, 28, 35, and 40mm. The lens exudes quality from tip to tip.You may tolerate heavier lens or may not mind lesser build quality of cheaper lenses. A walkaround lens will be used very often, so make sure you will be comfortable with it.This lens is famous for saturated color and deep contrast. Its images are simply stunning. At 17mm wide angle, barrel distortion is noticeable but relatively mild. From 24mm to 40mm, its images are distortion free and perfectly suited at capturing people.Vignetting (corner darkness) is minimal with mild chroma abberrations (color shadows). At f/4 aperture, details become noticeably softer toward the edges. The center region is very sharp and at f/5.6, edges remain fairy sharp. Thanks to 7 diaphragm blades, this lens can produce very nice bokeh at 40mm (blur effects).One of the most cited weaknesses is the f/4 aperture. In my experience, a bump in the ISO speed and steady hands are all you need to take well focused images indoor. On the other hand, if you are shooting with very little amount of light, you might wish for f/2.8 or image stabilizer. Although the difference between f/4 and f/2.8 is just 1 stop, my other lens, Canon EF 24-70mm f/2.8L USM (too heavy to be my walkaround lens) easily outperforms in such challenging situations. But by and large, I was not handicapped by the f/4 aperture.Some of the main competitions (sorted by price):- Sigma AF 17-70mm f/2.8-4.5 DC macro: Good zoom range with macro, and generally solid performance if you can get a good sample. It does suffer from a bit slow focus mechanism, soft corner, and chroma aberrations. Works only with EF-S mount.- Sigma 18-50mm f/2.8 EX DC: Very good value for f/2.8 aperture, but Tamron's 17-50mm is a bit better lens overall. Works only with EF-S mount.- Canon EF-S 17-85mm f/4-5.6 IS USM: This "traveler's lens" has a wider focal range than most wide angle lenses (widest among Canon) and is equipped with an image stabilizer. While it is a Jack of many trades, it is the master of none. Every lenses on this list will perform better at particular focal length. Then again, none of the lenses on this list has as wide focal range. It is famous for extreme barrel distortion at 17mm and chroma aberrations. Works only with EF-S mount.- Tamron SP AF 17-50mm f/2.8 Di II LD Aspherical (IF): This is the most direct competitor. It takes sharper images with faster aperture while costing less. Both the build and focus mechanism are significantly worse, but should be good enough for many. Works only with EF-S mount.- Canon EF-S 17-55mm f/2.8 IS USM: This is THE reference, if you can afford it. Its images have razor sharp details and great performance all around (minus vignetting, which is typical of EF-S lenses). The build quality is worse than L-series but still pretty good. Works only with EF-S mount. This is the best EF-S lens hands down.- Canon EF 16-35mm f/2.8L USM: One of the most expensive wide angle zoom lenses. It's larger and heavier, but has f/2.8 aperture.This is how Canon EF 17-40mm f/4 USM stacks up.Pros:- Among the very best build quality.- Excellent, buttery smooth, super fast front-focus system.- Top notch color and contrast. Very sharp center resolution.- Almost non-existent vignetting, generally low distortion, and well controlled chroma abberrations.- Ideal weight and size for walkaround purposeCons:- Edge softness at f/4 aperture.- Narrower focal length than most competing lenses.- Slower than some third party lenses.All in all, this is an excellent wide angle walkaround lens. It may not offer the most bang for the buck, but if you value full frame compatibility (EF lens mount) and excellent build quality, this is the default choice. This lens comes with a nice pouch and a lens hood. I find the hood to be somewhat ridiculously shaped and because the lens is resistant to flare, I do not use it often when shooting outdoor.

When I read the news of Canon releasing a new Mark II version of this lens the first thought that came to my mind was why? Has Canon lost its mind? Why would you mess around with a lens that has become a staple of nearly every professional Canon user in the world? Since this lens was released in September of 2001 it has earned a reputation as being one of the most rugged and sharpest lenses of its kind. Professional photographer and photo equipment reviewer Ken Rockwell, for example, borrowed this lens from a friend to test who had dropped it off an elephant to the cobblestones nine feet below while shooting in India. Even with that event in its history Ken gave it a stunningly positive review! Many of the most famous photos taken in the last nine years were taken with this lens, including many of the photos that appear in Canon's own sales brochures. In the lens life cycle, if such a thing exists, this lens is hardly an old timer at nine years old. With its proven powerful robust image stabilizer, legendarily sharpness, and tank-like build, one cannot help wonder what the motivation for fixing something that's not broke is. I think the real motivation was keeping "pace" with Nikon and raising prices.Canon is seen more and more as falling behind its nemesis Nikon. With the recent release of Nikon's VR II vibration reduction which supposedly can work up to four stops, Canon had to fire back with a "new" version of the image stabilizer on its own lenses. Thus IS II was born. Needless to say, the new Nikon 70-200 lens retails for over (...) on Amazon as opposed to this "old" Canon lens which sells for about (...). It's expected that new Canon 70-200 2.8L IS II will retail for at least (...) if not more. Is the new lens really worth (...) more than the old lens still being sold? I own this "old" model now for about six months and the only way I can see improvement is if somehow Canon could recreate this same lens, ruggedness and all, at half the weight. Now that would be something worth paying (...) or more for! In reality, the new model will actually weigh 20 grams more than the "old" model. So much for progress!I have shot indoor and outdoor shots both hand held and with my Bogen automatic mono-pod with this lens. In both cases the results have been nothing short of amazing. Clear sharp images almost every time with magnificent color and superb brokeh (blur quality). The image stabilization is first rate and runs hard and strong. Don't be fooled into saving money buying the other versions of this lens. If you ever expect to be free from using a flash and get great results in reasonable natural lighting, this is the lens to buy. If you can't afford to buy this lens then save up for it. If you compromise you may be sorry later.I believe that any changes Canon has made to the new lens will largely be undetectable by professional and amateur photographers alike. The only exception to this is the added weight, increased price, and the very slight ability of the new model to focus closer (about 8"). It's also hard to see how the current powerful image stabilization could be made much better. At some point it all becomes a matter of subject movement and no stabilization system can deal with that other than using higher shutter speeds. That said, the more important question to ask is whether Canon produced a "better" lens at all? Currently we have no test reviews to look at and it is entirely possible that the new lens may actually under perform this "old model". We just don't know at the moment. For my money I would grab this "old" model while you can. Not only is there hardly any risk, but in all likely-hood the after market value of this lens may soon rise.MY UPDATED COMMENTS: Despite some new positive reviews on the new lens, I still doubt that most will notice much of a difference between the new and the old lenses unless they really blow up the image. The old lens produced images that graced some of the top publications worldwide for the last 10 years with nothing but praise. Canon has effectively fooled you all to push though a huge price increase never before seen for an upgrade of the same type lens. It seems the consumer is once again the victim and they don't even realize it!

The canon adapter has been unavailable for a while, so I thought I'd try this one out so I could actually use my new R5. So far it works flawlessly!