Canon EF 100-400/4.5-5.6L USM ISThis lens is currently Canon's only L series telephoto zoom with IS (Image Stabilization). It competes with the 400/5.6L (no zoom, no IS), the 300/4L IS (no zoom), the 100-300/5.6L (no IS), the 35-350/4-5.6L (no IS) and the 75-300/4-5.6 IS (not "L" series). So how well does it compare?
It's a very well constructed lens, all metal (as far as I can tell). It has a smooth "push-pull" zooming action with variable friction, so you can easily lock it at any position
(no "zoom creep"). It has a plastic lens hood which bayonets onto the lens and can be reversed for storage. The lens has internal focusing so the length is constant (at any
particular focal length setting) and the front element does not rotate with focusing. It takes 77mm filters, weighs about 3 lbs and is supplied with a very nice soft case, much
more useful than the cylindrical hard cases Canon used to supply with their lenses (which usually ended up being stored in the closet rather than used since they were so large
How good is it?
Well, I tested it against a 300/4L and a 75-300/4-5.6 IS lens. Why these two? Because I had them on hand! Also they are probably logical alternatives to this lens, albeit in different price ranges.
I tested the lens by shooting slides (Sensia 100) of general scenes with each lens at the same aperture (f5.6) and focal length (100, 200 and 300mm for the zoom, 300mm and 300mm + 1.4x TC for the prime). I used a heavy tripod (Bogen 3051) and mirror lock up on an EOS 3. I marked on the slide mounts which shots were taken with which lens, then turned the slides over, shuffled them and tried to pick out the best, middle and worst quality slides of each shot. Once I'd sorted them out I flipped the slides over and looked at which lens was used for the shots in the three piles.
The results were really not a big surprise. The "best" shots were taken with the prime lens (300/4L) and the "worst" shots were taken with the 75-300/4-5.6. The slides taken with the 100-400/4.5-5.6L were in between. The 100-400 shots had significantly better edge quality than those taken with the 75-300, shaper and higher contrast with less (almost zero) lateral color fringing. In the center the 100-400 was sharper, though the difference wasn't as great as I saw at the edges. This applied at all focal lengths from 100mm to 300mm.
The shots with the 300/4L were the sharpest, both at the center and the edge. It would have been very surprising if this were not so. Even with a 1.4xTC (420mm f5.6), the prime lens still had an edge on the 100-400 at 400mm f5.6. Not that the shots with the 100-400 were bad (in fact none of the shots with any of the lenses were bad), just that the 300/4L shots were better.
The IS works as advertised, giving you about a 2 stop advantage in "handholdability" with IS on. There are two modes, one stabilizing in both vertical and horizontal planes for shooting static subjects and one which stabilizes on in the vertical plane, allowing you to pan with moving subjects. Note that IS does not guarantee you razor sharp shots with the lens hand held, but it certainly greatly increases the probablility of sharp images over a lens without IS.
The 100-400/4.5-5.6L is a good lens and if you only want to carry one lens to cover this range there is no better choice. It's certainly better than the 75-300 IS both optically and mechanically, just as you would expect from a lens costing $1000 more and using "L" glass (though it is also larger and heavier). It's not as sharp as the 300/4L prime lens and, though I haven't tested it directly, I'm sure it wouldn't be as sharp as the 400/5.6L either, but it is a lot more versatile. The 100-400 can also be pushed to 560mm (f8) with a 1.4x TC and 800mm (f11) with a 2x TC. I wouldn't say the optical quality is stunning at these longer focal lengths (especially with the 2x), but it's not bad and if you really need to go that long and you can tollerate a drop in quality, at least you have the option!
One drawback of the 100-400 compared to the 300/4L IS is that it is a full stop slower at 300mm (f5.6 vs f4). If you're shooting in low light using a tripod or you're shooting a moving subject, that extra stop of shutter speed could matter. Of course if you're hand holding the lens the IS function will give you about a one stop edge in "handholdability" at 300mm over the prime (2 stops at the same f-stop, but since the prime is a stop faster that drops to one stop if both lenses are used "wide open").
If lenses were cars I'd compare the 100-400 IS to an Infinity SUV, whereas the 75-300 IS is more like a 4WD Subaru and the 300/4L IS is more like a Mazda Miata (or maybe an Audi TT 4 Quattro!). The 100-400 does a little of everything and does it better than the 75-300 IS, but it doesn't do quite as well as the specialized 300/4L IS at being a 300mm lens. No shock there.
All of the alternatives have their own set of disadvantages:
Where to BuyAmazon carries most of these lenses at good discount prices, plus they offer free shipping an a no-hassle 30 day return policy.