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My Canon Extension Tubes Review

I have a set of Kenko extension tubes that I've used with three Canon lenses--the 85/1.8, 28-135IS, and the 100-400L. Here are the things I don't like about the extension tubes:

Adding extension tubes reduces the minimum focusing distance. It also dramatically reduces the maximum focusing distance. Saying that you lose infinity focus is an understatement--when I add extension tubes to my 85/1.8 lens, adjusting the focus ring on the lens changes the focusing distance some very minor amount, say, from 1 inch to 1 1/8" from the front element of the lens. You basically have to focus by moving the camera closer to or farther from the subject, or by adding/removing extension tubes. (Using a true macro lens solves this problem)

As you decrease the focusing distance, depth-of-field decreases dramatically. This means that you must use a smaller aperture to keep your subject in focus. Smaller apertures yield longer shutter speeds, which means you need to use a tripod. Your on-board flash won't work well--they make special, expensive flashes for macro shots. Here's a shot where I didn't have the option of using a tripod, because I had to stand on a bench to see into the nest. I used the smallest aperture possible that still gave me a shutter speed I could hand-hold, and as you can see, depth-of-field is very small. (URL may wrap to two lines)

Even at the smallest possible aperture, my 85/1.8 lens doesn't give enough depth-of-field for macro subjects. True macro lenses have very small minimum apertures, which reduces this problem. This picture of one of those tiny cactuses is a good example, because the front of the leaf is in focus, but the rest of the cactus is very out of focus--and the whole thing is only a couple of inches long.

With that said, I still keep the extension tubes around. Macro lenses are definitely better if you have the cash.