Macro extension tubes

On a whim at the end of last week I bought a set of Vivitar macro extension tubes for my Canon XTi. These are pretty neat: they pass through the auto-focus and auto-exposure signals from the camera to the lens, making them easier to use. There are three in the set: a 13mm, 21mm, and 31mm tube. If my mathematics is correct, this makes seven possible tube lengths since you can combine them in any order (call them A, B, and C, then the possible combinations are A, B, C, AB, AC, BC, and ABC).

Essentially extension tubes allow a lens (and I’m using the Canon EF 50mm f/1.8 as my experimental test bed) to focus a subject much much closer than normal by moving the lens further away from the sensor plane. Also they contain no glass at all (they’re hollow), so it’s the main lens you’re using that determines the quality of the photo. I will note that the depth of field is very small and the focus plane narrow. Still, for getting real close to a subject (and I mean real close) and having the subject fill the frame is amazing. Think flower photography for example.

Anyway, here’s Musaeus, our youngest cat, fast asleep:

This was taken with the smallest tube at a distance of some six inches – it’s a wonder he didn’t awake. It has not been cropped (the original is 2592×3888 pixels). It’s hand-held too and shows to a certain extent (1/15 sec at f/5.6, ISO 100); I think for this kind of work I’ll just have to use a tripod.

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