Canon 75-300 and 100-300 lenses

by Bob Atkins; created about 2000

Canon currently make 3 basic "300mm telephoto zooms", the 75-300, 100-300 and 100-300L. At one time or another, I've used all of them, so I think I'm in a reasonable position to make a comparison.

EF100-300/5.6L

The EF100-300/5.6L is the only lens in this group which uses fluorite or UD elements (it has one of each) to achieve "apochromtic" status. It's an old lens, introduced very early on in EOS history, which means the design hasn't changed in the last 10 years. No USM, no fulltime manual focus, rotating front element, push-pull zoom, no tripod mount. It's a constant f5.6, which means it's a stop or so slower than the other lenses at the short end. It's sharp at 100mm and the sharpness holds up well (though does drop a bit) at 300mm. This was one of the first EOS lenses I owned and I was fairly happy with it until I bought the 300/4L. The 300/4 was not only nicer to use (USM, no rotating front element, full time manual focus, tripod mount), but is also a stop faster and sharper! I sold the 100-300/5.6L shortly afterwards. Overall the 100-300/5.6L is a decent lens from an optical standpoint, but the ergonomics leave something to be desired. I don't really know why Canon hasn't upgraded it, or if they ever will. A 100-300/4-5.6L with USM and tripod mount could be a winner for those who need a sharp zoom. Perhaps the new 100-400/4.5-5.6L IS fills that gap, but at a cost $1000 more than the current 100-300/5.6L
 

EF100-300/4.5-5.6 USM

This is Canon's mid range consumer zoom of the trio. It's a current design with a ring USM, fulltime manual focus and a non-rotating front element. Focus operation is silent and fast, as you would expect. Optically it's pretty good at the short end, dropping to OK at 300mm. Clearly a couple of notches down on the 300/4L and a notch down on the 100-300/5.6L at 300mm. If you want real resolution numbers, at 300mm and on on Kodachrome 25 at f5.6, the 300/4  resolves around 80 lp/mm, the 100-300/5.6L about 70 lp/mm and the 100-3004.5-5.6 about 60 lp/mm, all under optimal conditions and in the center of the image.
 

EF75-300/4-5.6 (II, USM, IS)
 

The 75-300 is available in 3 flavors. The "II" uses a micro motor (not USM). The USM uses a USM motor (no big surprise), but not a ring USM. It uses a micro USM, so it doesn't have full time manual focus. It's not silent either, though it's pretty quiet. I'm not quite sure just what the advantage over the "II" is. Maybe it's slightly quieter? Maybe it's slightly faster focusing ?(I never compared them directly). It costs $20-$30 more, which isn't really a lot. Personally I wouldn't worry about which version to get too much. If your budget is real tight, get the "II", if not, get the USM. The front element rotates in both versions and optically they are identical. The lens formula is very similar to the 100-300USM, but you get a little more zoom range. At 75mm it's very sharp. It will resolve 80+ lp/mm on Kodachrome 25 in the center of the frame at f5.6. The edge is a little softer, but still OK. At 300mm as far as I can tell the resolution is the same as the 100-300USM. In the 100-300mm range, there's very little difference in the optical  performance of any of the 75-300 lenses and the 100-300 USM.

The 75-300/4-5.6USM is also available in an image stabilized (IS) version. This lens has built in gyros and a sytem which corrects for unsteadiness when hand held. Typically this enables the user to get sharp images with a 2 stop slower shutter than the non-IS lens. So if you think you can hand hold a 300mm lens at 1/350 and get sharp images, then you should be able to hand hold the IS lens at 1/90 and get equally sharp images. Very useful if you don't use a tripod or you are shooting from a moving boat or an airplane for example. The optically performance of this lens appears to be very similar to the non-IS version despite the extra elements needed for the IS function. I tested the two side by side and saw no significant difference.
 

What to buy?

If you need an IS lens because you shoot in low light or with slow film and you refuse to use a tripod, then there's only one choice. If you want the best possible optics in a zoom, get the 100-300/5.6L, though personally I'd get the 300/4L if you intend to shoot much at 300mm. If you want the ring USM, fulltime manual focus, a non-rotating front element, silent operation and fast AF, get the 100-300USM. If you really need the extra range 75-100mm or have a VERY limited budget, get the 75-300. The II if you cant afford the USM, the USM if you can!
 

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