Verdict:If you need 100-400mm on a Canon EOS camera, buy it! This is your best bet!!If you need 300mm or 400mm and are on a budget, buy it!If you need a Zoo or air show lens this is it, buy it!You won't be disappointed!!4-27-2009 I just got back from photographing the World Premiere of X-Men Origins: Wolverine and once again the 100-400 IS L lens was awesome. I ended up mainly using two lenses the Canon 24-70 F/2.8 L zoom and Canon 100-400 IS L zoom lens with most photos taken with the 100-400. When you have only one chance to get Hugh Jackman riding by on his Harley you want to make sure you have reliable quick focusing equipment. Plus a lot of times you just can't get any closer to the action like at a World Movie Premiere, it's times like that when you absolutly need a zoom and the 100-400 IS L is one of the best! [...]01-03-09 Canon 5D Mark II Update:Canon 100-400 F/4.5 - F/5.6 IS L lens. This is the second most used lens in my 5D Mark II arsenal. This lens was my biggest surprise and is not only tied for second place with the Canon 135mm F/2 for sharpness but is amazingly sharp wide open. It's a monster of clarity at F/7.1 like it never was on my Canon 40D. It also becomes useable on the 5D Mark II in wider shot situations where on the 40D it was only usable as a longer lens. Sporting the longest zoom range of any Canon zoom this lens has to be without doubt the finest Zoo lens ever made. You can frame almost any animal in almost any exhibit perfectly. This is also my lens of choice for taking photos of people at events and aircraft at air shows with the 5D Mark II and is the King of versatility on a full-framed sensor camera. This is my sharpest and clearest zoom lens by a long shot (no pun intended. It's as close to the you are there feeling of the 85mm F/1.2 lI lens as any zoom lens I have.After an extensive battery of tests both hand held and tripod mounted I have come to the following shocking conclusions.The Canon 100-400 L zoom is almost as sharp at F/8 as my Canon 85mm F/1.2 at F4 and that's saying something!!!Slightly sharper at F/8 as my Canon 70-200 F/2.8 and that's saying something to!!!I may have a very sharp copy and I hear there are soft copies out there. Make sure and buy yours here at Amazon.com where you can return the lens if its not as sharp as you thought.Pros:Super Sharp!Very versatile!Great ContrastGood bang for the buck100-400mm SWEET!This is the perfect Zoo lensThis is the perfect Air Show Zoo lensThis is the perfect Renaissance Festival lensAttracts a lot of attention, you will be asked if you are a proImage stabilizer lets you get away with crazy like shutter speedsSweet Bokeh at subject filling close range and at all ranges on full frame sensor cameraRaw photos respond well to sharpening and contrast / colors in Canon Digital Photo professionalCons:Can be heavy for the uninitiated!Does draw dust into your camera when zoomed!Old style image stabilizer must turn off on tripodZoom locking ring is attached to the manual focus ring.No weather proofing, a strange thing for an out door lensAttracts a lot of attention, you will be asked if you are a proPulls dust into lens around the zoom ring when zooming in and outSlow auto focus compared to other L lens, slower then all of them except my Canon 85mm F/1.2 L IIStrange black hole if you take a photo when jerking the lens to track a birdLens sometimes seems to slow cameras response when taking a photoOn cropped sensor cameras only strange variable looking Bokeh at some distances especially when stopped down and in sunlight with contrasting lines like branches. Wonder bokeh no full frame camera (5D Mark II)I gave it only 4 Stars because of the crazy way the zoom friction and manual focus rings are together and lack of weather sealing and variable Bokeh. It takes a dedicated photographer familiar with the lens to get consistent because of the variable Bokeh. Separate the manual focus and zoom friction rings, give it weather sealing, updated IS and great Bokeh at all settings and ranges and I would have given it 5 stars!Introduction:Longer range and versatility that's what I needed for my Canon 40D. What good is a prime if you don't get the shot at all? I mean I love my Canon 135mm F/2 it has the best Bokeh in the world along with my 85mm F/1.2 but it's a little short for birding even on a 40D and after renting a Canon EF 500mm f/4L IS you know what the meaning of heavy (8.5 pounds) and specialized mean.Plus there's nothing like having a zoom, take time to change out that lens during a renaissance festival and you just may miss a once in a lifetime shot.My 70-200 F/2.8 L is a great lens but the zoom range is way too short at times like these. I want something with much more zoom capability.I wanted something I could take to the zoo and gets shots both near and far and the same at air shows and the renaissance festival and maybe even a football or soccer game or rodeo and all without a time consuming dust introducing lens change. At the festival you can go from a knight and damsel group portrait shot to a close up of a bird of prey flying by in a second and without changing lens. At an air show you can be shooting the crowd waiting in line to board a C5 Galaxy cargo plane and in the same minute swing up and get an F-16 cockpit shot as it roars by. On a cropped camera you are at 640mm and into serious birding territory on a full framed hey you still have 100-400.First shots:OK, I must have gotten a really good sample because after sharpening the Raw files in Canon Digital Photo Professional (DPP) this lens is sharp at all zooms and very sharp indeed stopped down to 7.1 between 300 and 375mm. No complaints there that's for sure!! It's very close to my Canon 70-200mm F/2.8 in it's sweet spot.Zoos:WOW!!! I visited the Phoenix Zoo this last Saturday with my Canon 40D and this new Canon 100-400 IS L zoom and all I can think of is wow!! Where have you been all of my life? With a zoom range of 160 to 640mm when mounted on my Canon 40D you can't go wrong. And with the image stabilizer IS you can literaly stick this camera in auto ISO and walk through the entire zoo with just one lens and get great closeup shots of everything. Need a portrait of that Tiger while he's walking the back wall as far away as he can get? No problem, zoom out to 400mm which equals 640mm, here kitty kitty kitty. And how about the Flamingo's right up next to the fence and you want the whole group, just zoom back to 100mm and bingo!I wonder why I hadn't purchased this lens from the start. No dust educing, time eating lens changes required, just go through every exhibit with the one lens picking off animals one by one or in groups. It's like shooting fish in a barrel, yeee haaaa!!!Notes:Seems sharpest at 375mm and F/7.1 and F/8Variable Bokeh, can be the best or worst depending on use (see Bokeh below)Air (and dust) seems to enter and exit around zoom ring as you zoom (NOT into and out of the camera sensor as some would have you believe).Review:This lens takes some getting used to, it's different: longer, more complicated, push pull zoom and IS make it a little more complicated then the other lenses I have.The first few shots I took with it were rather disappointing but then I started finding the groove for this long-range photographic weapon and when used in that scope you can score some really fantastic jaw dropping photos.Overall my Canon 70-200 F/2.8 seems to make a slightly more pleasing photo at times and at other times the 100-400 does. The 70-200 as more consistently pleasing Bokeh. But the 100-400 200mm longer. The physical size when the 100-400 is at 100mm is very close indeed and the weight feels close to the same in the hand with the 70-200 feeling slightly lighter.The strange thing I find too is the zoom locking ring and manual focus ring are attached to each other and change position as you zoom in and out. This makes for a little confusion when reaching for it at first as you never know where it is when quickly reaching for it while keeping your eyes in the viewfinder. That and if it's tight at all you have to take both hands to release the tension and move the zoom where you want.The Groove:Make sure you have the IS in the ON positionShoot with plenty of light and hold her steadyShoot between 300mm and 375mm at F/7.1 or F/8Make sure focus limiter switch is in the correct positionShoot in Raw and process in Digital Photo Professional (DPP)Don't be afraid to push the sharpness and color way up in DPP as neededPractice Practice Practice if you are shooting digital then you can practice plenty.Image Stabilizer (IS):I have taken HAND HELD SHOTS at 1/10s and 1/6s even zoomed out to 400mm of the neighbors house and car down the street and they came out so well you can read the license plate! I set my 40D to 3200 ISO and wide open aperture then simply propped my elbows on top of the trash can and took some night shots to see what this lens could do. I couldn't do it every shot only about 1 out of 5 to get my breathing and the timing of the shot right but the fact that I could pull these shots off at all is incredible!!!To get consistent shots I in better lighting conditions I have found with my elbows propped I can consistently pull off 1/30 second at 400mm which works out to 640mm on a 40D! With un-propped arms I could pull of 1/60 second at 400mm. This alone should be a good reason to buy this lens.Bokeh:On full frame cameras like the Canon 5D Mark II the Bokeh is great. At close range it's almost as good as any lens I have. Well except for maybe the Canon 85mm F/1.2 II L. But over all it's great.But, if you are using this lens on a cropped sensor then be sure to read the next paragraph.How could one lens have such fantastic Bokeh in one shot and such strange horrible Bokeh in the next? Up close with frame filling subjects near wide open aperture the Bokeh is a dream, but shoot at further distances with a cropped sensor camera like a Rebel or Canon 40D/50D etc with branches as a background stopped down so you can see some detail there are weird lines around each item. Shooting aircraft or birds in flight this is no problem as the background is just sky, but distant birds in trees with some leaves and limbs out of focus and the photos can look very strange.Lens Vignetting (Light Fall-off)Light fall off in the corner of your photos or vignetting is no longer a problem for any Canon lens on the newer Canon Digital Cameras like the Canon Rebel XTi, XSi, 40D/50D, 5D Mark II as the Vignetting can be corrected automatically in-camera and with Raw photos in Digital Photo Professional (DPP). You can even adjust the amount of correction to your photos as needed with Raw photos in DPP, sweet!!!In flight tips:Shooting in-flight birds and planes with this lens then follow these tips.Shoot in bright lightSet minimum focus switch to 6.5 metersTurn Off IS if you have enough light, the auto focus seems a little faster without itSet Auto Focus Mode to AI Servo and Drive mode to maximum frames per secondSet exposure compensation to +2/3 stop especially for darker birds or bird will be underexposedMake sure shutter speed will be at least 1/500s or faster set aperture and or ISO as needed I usually end up on Auto ISO on my 40DPre-focus on something similar to the distance of the target bird or planePull zoom back to 100mm to ease acquirement of target bird then zoom as needed towards 400mm while trackingStart shooting as soon as a decent focus and composition of the bird is acquired (DON'T wait for the perfect composition)If needed try looking over the top of the camera and down the top of the lens barrel and try to acquire the bird first then look through the lens.Once acquired hold down the shutter and keep firing off photos as you never know which shot will be a keeper.Push / Pull ZoomThis is a love / hate affair because I love the way I can quickly zoom from 100 - 400mm very rapidly, but...The friction ring to adjust the tension of zooming is attached to the manual focus ring. This means you can't simply reach forward and grasp the friction ring and adjust it with one hand. No you must hold the lens with two hands one holding the focus ring and the other the friction ring and then adjust.The friction ring and manual focus rings both move back and forth with the front part of the lens when you zoom. What this means is when you are in the heat of battle you can't always reach forward by feel and do a manual focus as the distance out on the zoom where the focus ring is located is highly variable.I don't know if it's possible but if it were I would have Canon redesign the zoom ring and the focus ring separate. This would allow me to reach up and adjust the friction ring by touch without having to hold the manual focus ring to keep both from just turning. And to adjust the manual focus without tightening up or loosing the friction ring.Anyway the whole process takes a little while to get used to especially for those of use coming from say a 70-200 F/2.8 zoom where I can always just adjust the zoom of the lens a little with no thought and without taking my eyes off the subject from the viewfinder.Uses:Any outdoor photography where you need a wide focal range in a really short amount of time and can't always get really close to your subject but need a close up of it. Zoo's, Air Shows, Renaissance Festivals, Rodeos, Football, Baseball, Soccer I can think of lot's of tests in the coming weeks for this lens and I intend to hit every one of them.Verdict:If you need a zoom with more reach then your 70-200 then this is your best option. Try it and you just might like it.Updates:As usual I will be coming back to this post and giving updates on my use of this lens. I have Canon a 5D Mark II on order and will update with how this lens works on a full frame body. Should be a whole another world.11-04-2008 Update:I have found that by taking the tripod mount off the lens is much more comfortable to hold and you can get to the zoom friction lock ring and the manual focus ring much easier. The IS on this lens makes a tripod an option not mandatory and when out photographing wild life hand holding is much easier.11-05-2008 Update:I put all my longer lenses up against the Canon 100-400 in a battery of tests both hand held and tripod mounted and was amazed at the results. At F/8 where it's sharpest Zoomed to 135mm and 200mm it's as sharp as my Canon 135mm F/2 prime and my Canon 70-200 F/2.8 zoom. And it has better contrast then the 135mm F/2. Both the 135mm and 70-200 have better Bokeh though but I was surprised how useful the 100-400 with IS can be in low light as long as the subject is motionless. I have found with practice and bracing I can consistently get good sharp photos at 400mm at 1/30 second and have scored a few shots as slow as 1/6 second by bracing both elbows putting the camera on high speed and shooting 6 shot bursts. One or two of the middle shots are always sharp. Simply amazing!! So if anyone is telling you this lens is worthless on a darker day or at sunrise or sunset they just don't know this lens. I have found even getting pretty sloppy you can get consistent shots at 400mm at 1/200 second. Next earl morning shoot at the bird sanctuary this 100-400 is the lens I am bringing.11-07-2008 Update:I have found that you can actually rotate the tripod mount up 180 degrees so that it is facing upward and out of your way but still have it on the lens. Could be handy if you want to have the mount with you but not in the way when using the lens.11-12-2008 Update:The more I use this lens and get used to it the more I love it. I can't see myself without it now. I am totally used to the push / pull zoom and now actually like it better.12-2-2008 Update:Found this interesting information and thought I would pass along.The Canon 100-400mm F/4.5-5.6 L IS also has fluorite and Super UD-glass. Fluorite has very low dispersion so the 100-400 exhibits less chromatic aberration than if it were made of ordinary glass. The fluorite lens element aligns the points of focus of the three primary spectral colors of red, green and blue to meet at one point for ideal correction of chromatic aberration. Also included is UD-glass, which is a special type of optical glass whose properties nearly match those of Fluorite.Bottom line on the fluorite and Super UD-glass, you get the best possible image even though you get a huge 100-400mm zoom range!1-30-2009 Update:I just bought a new Zoo membership and took my daughter with me on my second visit to the zoo. She brought another lens along and quickly wanted to borrow the 100-400. There was no going back she didn't want to give it back and clicked off one perfect photo after another including the Male Baboon photo I posted with the photos here. I am so sold. Can hardly wait to try this lens at the Renaissance festival next weekend.5-26-2009 100-400 update: So I came back from the Riparian Bird Preserve yesterday where it was rather dusty and I noticed that my sensor and mirror box were full of dust. I decided to do a test on my 100-400 lens and sure enough it does pump dust into the camera body.If you turn the zoom friction ring all the way loose and zoom in and out with the bottom end cap off there is no resistance. If you put the bottom end cap on tightly and zoom you can feel resistance. Then if you loosen the end cap just a little you can actually feel air being sucked in and out around the end cap as you zoom in and out.Thank God for my FIrefly digital sensor cleaning system! Be forewarned if you own this lens you will need to take care in dusty environments.6-27-2009Still very in love with this lens. You can see a lot the photos I have taken with it at a web site called flickr. They won't allow me to put a link here anymore but you can go to flickr and search for my name Grant Brummett then look through the photos. I used this lens for the majority of the photos in my Wolverine X-Men movie premiere set.Lenses I currently own:Canon EF-S 17-55 F/2.8 IS Ultra sharp, great colors, great low light, poor zoom actionCanon EF-S 18-55mm f/3.5-5.6 Rebel XTi Kit lens Muddy, slow, pile of junkCanon EF 17-40mm f/4 L Fantastic colors, sharp zoomed 17 to 24mm, ultra smooth zoom action, light weightCanon EF 24-70mm f/2.8 L Fantastic colors and contrast, sharp zoomed 40 to 70mm, zoom a little stiff at first, heavy, repair prone!Canon EF 50mm f/1.8 II Good budget portrait lens, light weight, disposable, sharp from F/2.5Canon EF 85mm F/1.2 L II The best portrait lens for female and children clients, buttery smooth Bokeh, heavy and expensive it shares sharpness with 135mmCanon EF 135mm F/2.0 L The best portrait lens for males and tied with Canon 85mm F 1/.2 for sharpest lens I own, buttery smooth BokehCanon EF 70-200mm f/2.8 L fantastic colors, sharp for a zoom, very versatile ego boosting and attention getting and heavy! My favorite zoom lens!!!Canon EF 100-400mm f4.5-5.6L great IS, super colors, sharp for a zoom, extremely versatile, variable Bokeh, even more ego boosting and attention getting when extended and 400mm reach, will pump dust into your camera body.My next lens purchase I'm saving for right now: _Canon EF 300mm F/2.8 IS L the finest lens ever