CanonEF 100-400mm f/4.5-5.6L is USM Telephoto Zoom Lens for Canon SLR Cameras

I bought this lens about a week ago. I've taken about 1000 pictures with it since, including a trip to the Dallas zoo. I've been pouring over the pictures, and I'm impressed with how well this lens works.I also have the Sigma 150-500 f/5-6.3 APO DG OS HSM lens, so much of what I mention here will be as a direct result of comparing the two lenses.First, the thing that I like most about the Canon 100-400L is that you can use it wide open. Sure, it sharpens a little bit if you stop it down, as do all zooms. But it doesn't change that much! My Sigma, for instance, at 500mm, f/6.3, is too soft by far! If you stop down to f/9, it's usually acceptable, but I wouldn't say it's "sharp" until f/11. At shorter focal lengths, it isn't this bad...at 400mm, you can get some pretty decent shots at f/8, but even then, it continues to improve until f/11, f/13.... My new Canon, on the other hand, is 100% acceptable at 400mm/f5.6. It gets a bit sharper by f/7, but it's not a big difference. And the differences are small enough past that aperture that it's hard to say there's an improvement at all. The bottom line for me is that there's much less chance of me missing a shot because I forgot to step down two stops...or because I couldn't open wide enough to get enough exposure!It's also almost 2" shorter, and almost an inch smaller in diameter, than the Sigma. Lengthwise, it's about the same as a 70-200 f2.8, and weighs just a tad more. So, if you can fit a 70-200 f/2.8 in your bag, you can probably fit this. I carry this lens mounted on the camera using a Black Rapid strap attached to the tripod collar. Carried this way, you forget you have a 400mm zoom lens attached...or maybe I'm just used to the Sigma (which is longer, and weighs a pound more). At any rate, it's not a small lens, but it's not unmanageable.The auto focus is noticeably faster than my Sigma, and worked well. Out of 500 pictures taken at the zoo, there were maybe 20 that I'd say weren't in focus, and some of them were due to me not having a fast enough shutter speed, in spite of the Image Stabilization.And speaking of IS, it works pretty good on this lens, even thought it's only good for about 2 f-stops. Remember, this lens design is over 10 years old...and back then, 2 stops was state of the art in IS! This is one area where the Sigma beats the Canon..the sigma has a better IS (though Sigma calls it OS). But really, if you're spending this kind of money on a 100-400mm zoom, you probably have already realized that IS isn't going to save you from bad technique, or stop your moving subject!I have used it with a Kenko Pro300 1.4x Teleplus teleconverter. I can't say there's no loss in sharpness, because of course there is. But it's still usable...here, it DOES pay to stop down a bit. The autofocus still works with the TC on my 5Dm3, though it's a bit slower.Some folks hate the push-pull zoom mechanism, but not me! I love it! It's fast, and easier for me to adjust to a moving target. The only downside is that there's no lock! If you carry it without tightening the tension ring, the lens will extend on its own. You can tighten the tension ring so that this doesn't happen, of course, but working the tension ring is a two handed job. In fact, that's my only real gripe about the lens...I can't go from locked (or more accurately, tight) to loose one-handed. But, I'll live with this because I like the lens so much in other ways.It comes with a case, a hood, and a tripod collar. It should...it cost enough. The case is pretty nice, and the tripod collar is first rate! The hood is OK...but for some reason seems kinda 'plastic-y', although in typical Canon fashion, it does have the non-reflective suede on the inside.In this focal length range, you really only have two choices, for a zoom lens...this lens and the Sigma. You can get good results with the Sigma, certainly! But better results, and with less effort, are the norm for this lens.

First, I just want to say... I waited most of my life to get to the point where I could take professional quality pictures. Now that I am there, it is indeed everything I wanted it to be. I'm loving this. :-)This lens came to me because I accidentally dropped my 75mm-300mm non-IS non USM lens in the Gulf of Mexico while shooting the sunset at Lover's Key State Park, Florida. Some would argue that I probably did this on purpose just because I was sick of the poor quality of that lens, and although I do share your sentiments, I assure I did NOT do that on purpose. It *was* funny in its own way, but after realizing just how much damage was done to the internals and realizing I'd have to replace it, I was in fact quite horrified. I will quickly say this for that lens - it CAN yield good pictures, IF you know how to work it. Keep your aperture around F13 and stick to bright light, and it will produce...BUTIt is NOT a pro lens, and it will NEVER be a pro lens. I took over a week to convince myself to put down the huge money for this "L" telephoto lens, and it took me about that long again before I was sure I'd done the right thing. I am sure now, more or less, but the painful expense still haunts me. That's one thing you have to get over if you want to take exceptional pictures - good images do in fact require good optics, and good optics COST. That's how it is currently, and you have to deal with it or do without. The plus side is the resale value on an L lens is HIGH if you treat it right, so if one day you need your money back out of it, you can get most of it back just fine.When I finally got my new lens, I was immediately shocked by the size and weight. Unless you've seen or held one before, you're going to be intimidated. Honestly though, on my first long outing, I came to find that it is NOT that bad, honestly. Make sure that your shoulder strap is wide, and you won't be bothered by it that much. I keep my camera crossed over to my other shoulder like an ammo belt, and the camera and lens lay nicely against my hip, even when I am walking fast. I can very quickly grab the camera, slide it up to my eye, hit the power slider, and shoot within seconds. The birdies never see it coming, pow.Now, I should add here that my combo is a Canon Digital Rebel XT and of course my new 100mm - 400mm L F5.6 IS USM.The first time I shot at all with this, I was disappointed and worried that I made a big mistake. Yes, I was making a mistake, but not in the purchase, just with what to expect from the lens' behavior compared to the 75-300mm that predeceased it. This is NOT that lens by any stretch, and the major differences combined with a mild concussion from a whoops at my workplace led me to bad assumptions and generally poor thinking on how to use it for a given scene.1) Aperture on this lens does not behave like aperture on that 75-300. With that cheaper lens, aperture has a dramatic effect on sharpness. Not nearly as much with this lens.2) The extra focal length means that any motion in the image can create blur if your shutter isn't fast enough. Make sure you've got lots of light if you are shooting moving objects.3) IS only corrects for camera shake, NOT for subject motion. Don't go into a dimly lit scene expecting IS to save you with moving things in the frame, it won't work. Open the aperture as far as you dare, keep your ISO fairly high, kick the IS on to reduce your own movements, and then just take a LOT of shots. Not understanding or appreciating this simple fact of photography cost me a lot of good shots that first time out, and today when I go back I will definitely be better prepared.4) Learn to treat the lens as if it is the main component of the camera. Don't go trying to attach/remove/adjust the lens as if the camera is your anchor... Believe me, this thing makes my Rebel XT feel like a toy, and if you misjudge the weight of this lens, it could slip out of your hand and really embarrass you. Respect the lens, definitely. No, I have NOT dropped my lens yet... are you kidding??? $1400!!Now that that is all out of the way, let me tell you why I will die before I ever let my new lens go:The images, omg... I never knew I could take such amazing pictures with my Rebel XT and honestly now I know I won't replace the camera body with anything better until the shutter dies in it. After I got my head better around shutter speed and lighting, the good images were simply incredibly good. Even with a Bower 2x Teleconverter, the better images are way better than even the 75mm-300mm could do. It's the contrast, color depth, and sharpness... this is a professional level lens and my God does it show, and I don't have to stop down to F13 to get good sharpness. :-)The IS is a wonderful tool, believe me. If you can get your subject to hold still, and you have reasonably stable hands, you can pull off great pictures at 1/30th of a second shutter time. I'm serious. It's more in what is moving in your scene than how steady you are, so long as you don't try for senselessly long exposure times. I love the IS and I am SO glad I held out for a lens that has it.The USM autofocus is just... wow... After so long of shooting with a lens with no USM, this is like having my cake with a double shot of apricot brandy with a little umbrella in it. When I go shooting at the beach, I am there primarily to shoot the wildlife (sea birds). When I'd shoot a bird in flight, I would take many exposures in hopes that one would turn out and be a good shot. This time out, I did that same thing with the new lens and I was amazed to find that I was getting intact sets of images of each bird I did this with. One or two of the first shots would be a touch out, maybe, but several would be in sharp focus. The AF keeps up fine with moving targets, and this is something totally new to me. The focus motor is fast, silent, and tack accurate, MILES beyond the old cheapie I sank in the ocean. Detect a bit of sarcasm there? :-)The zoom range leaves a hole for me between my kit 18mm-55mm lens (yes I know, I have a crap lens for wide angle... you can help me fund another L-glass lens any time you like), but honestly I haven't missed it yet. I adore the long focal length of this lens and if there's a softness to the 400mm end then I haven't really seen it yet. In fact, I'm looking at a test shot I took today using the 2x extender and the new lens for a combined FL of 800mm... scary huh... and I am seeing great sharpness, surprisingly enough. Had the target been out of the shadows and in the sun, I'd say I could have pulled off a really good picture from it. Not bad for a 300' distant shot of a cute girl in a strongly shadowed stairwell at combined 800mm, 1/800th of a second (F8.0!) exposure time FREE HANDED. It's amazing what you can do with this lens when you really try.So... I've babbled enough, although I could go on all day. Here's the pros and cons.Pros:Very solidly built, feels like a tank shell.Amazing image qualityFast USM focusIS is GREAT when thought out beforehandManual focus ring is right there when you need itSliding focus rather than rotating is actually quite niceTension ring for focus is a great touchVery nice very solid tripod ring with bearings! How cool is that?VERY nice carry case... they really did do a nice thing with that.Cons:Heavy... wow heavy. Weighs like a tank shell too... But, it's a PRO lens, what do you want?Ok so it IS white... actually beige white, mine is. Believe me, if you still care about the color a week after using it heavily, you are spoiled and should shoot with an old Digital Rebel 300D plus 18-55mm kit lens ONLY until you regain your sense of perspective. It took me ONE DAY to forgive it for being white. ;-)It's BIG. Its so big that you will likely have to reconsider your entire outfit and how you carry everything around in the field. I find personally that the size of the thing is actually a bigger deal to me than the weight, surprisingly enough. If you have a Rebel XT or similar, the camera does look a little silly stuck to it, but here again WHO CARES... the images omg!!Sometimes you can forget that you are balancing the lens with a hand under the focuser, and accidentally knock your shot out of focus. Also, since the focus and zoom tension rings move as one, it's easy enough to de-tense the zoom while focusing. It's a learning process, and not all that terrible really.Canon, honestly... almost $1400US for a lens and no UV filter for the front. Maybe this is me being nitpicky but really... what would it cost them to provide you this very basic protection for your very expensive lens? Just be sure not to forget to get one... and make sure you remember this is 77MM threading, not 58 or anything else!One last comment:If you are like I was, and struggling to make a tough decision... perhaps this will help. This is a Black Oystercatcher on the beach at Lover's Key, shot at full 400mm from about 40+ feet or so away in terrible light and free handed - no tripod. Note the tiny water droplets on the feathers. Before I got this lens, I would have told you I wish I could do pictures like this one. Now I not only can, I AM. :-)ISO 200, F5.6, 400mm FL, 1/640 sec.[...]Make like N**e and just do it! :-)Edit: Update Jan 7, 2012 - Some months back, a strange thing happened to my lens. At least I thought it was strange until I read others' comments about the very same thing happening to them. The tension ring began to bind on me, making tensing the zoom difficult to impossible to do right. Then it happened - tiny bearings began to fall out. I tried to fix the problem myself but it proved to be way beyond my abilities. I ended up removing all the bearings, which of course defeated the tension ring entirely. To fix this would be very expensive, so I just go around with it as is. I still love my "secret weapon" gigantic tank-shell L-glass lens, how could I not, but I am less than impressed with the fact that this is a KNOWN problem with these lenses and Canon apparently couldn't see this coming enough to jump on the problem quickly so that it would fade into myth and people like me would have been spared the horror of over a hundred tiny ball bearings falling out of the lens. Long and short of it? GREAT lens... not so great job on the tension ring mechanism! I would expect better from $1400+ worth of optical hardware.Another Edit: Update March 6, 2013 - I decided to blow a lot of money and get myself a Canon T2i to replace my Rebel XT that shot the picture of the Oyster Catcher in this review. Thus is how I discovered the difference between 8 megapixels and 18. With the 8 megapixel sensor of the Canon Rebel XT, my photos with this beast of a lens were always very sharp unless I messed up the focus, and I never questioned just how sharp the lens actually was. With the much larger 18 megapixel sensor of the T2i, all of a sudden I'm looking at my pictures and thinking, "What the hell! None of these are razor sharp! Is my lens dying?!" Only recently did the epiphany hit me and I realized that what I was seeing was the greater resolution of the camera sensor exposing my weaknesses in fine focus. Oh... ok... so that's what reality is like? I never knew because I never had such resolution. I'm pleased to say that I still love my lens, and I had better for all the money I put into it, but reality is reality and with a much larger resolution to work with, you simply HAVE to experiment with your camera settings or get over it and accept some soft edges. I took a LOT of pictures last month, at the beach and other places, and I learned firsthand that aperture is everything. Keep it wide open to grab light, and you pay with loss of sharpness and a razor thin depth of field will drive you crazy at times. Keep your aperture tight, and you maximize your sharpness but you lose a lot of light. Sounds like it sucks, right? Well, yes, it does... but it's reality and it's part of real photography. In a lot of ways, this revelation has been very good for me and has added considerably to the richness of the hobby.[...]FL:400mm, ISO:1600, F-Stop:F/10, Shutter Speed:1/3200 second. In retrospect I should have shot at a slower shutter speed with 800 ISO for less noise. It's still not a bad shot. :-)NR417