For the past few months I have started routinely using extension tubes with my 100mm macro lens for photographing tiger beetles. I do this primarily because for most tiger beetles and other insects in the smallish to medium-sized range I need the capability to go both above and below 1X magnification, meaning that I must constantly switch between my Canon 100mm lens (1X maximum) and MP-E 65mm lens (1X minimum). With a full extension tube set (68mm), my 100mm macro lens effectively becomes a 0.7–2.0X macro lens, a nice range of magnifications for most of the photographs that I take. There is a secondary benefit to this in that the subject-to-lens distance is decreased somewhat, allowing me to get the MT-24EX flash heads closer to the subject for better lighting.
Lately I’ve been wondering what the magnification capabilities would be if I added extension tubes to the 65mm lens. With a maximum magnification of 5X, it hardly seems that even more magnification would ever be needed, but who knows what uses one might find if the capability exists. In theory, it seemed like it should work—after all extension tubes are simply tubes with no glass (in fact, the 65mm lens itself is simply a macro lens with a very expensive, built-in bellows). The only consideration was whether the focal plane would remain outside of the lens. Tonight I finally decided to sit down and try it out, and the results were really quite stunning. The three photos below show an ordinary pencil lead, the first with the 65mm lens alone set at 1X, the second with the lens set at 1X plus full extension tubes, and the third with full extension tubes and the lens set at 5X. The full extension tube set provides an additional ~1.7X magnification, making the 65mm lens effectively a 1.7–8.0X macro lens!
The subject-to-lens distance is indeed quite short—only about 38mm or so. However, having at my disposal an 8X macro lens suddenly opens up a whole new world of ideas for insect macrophotography. Knowing that the combination of 65mm lens and extension tubes is possible, I just had to try this out on a living subject—like now! I happened to have in a terrarium a subject from the day’s collecting, so I tried it out—again with the 65mm lens fully extended to result in 8X magnification. Shown below is a example of this lens combination at full magnification, completely uncropped—can you name the subject?
Copyright © Ted C. MacRae 2011