Can I use macro extension tubes with telephoto lenses?

Question

What I really want is an extension tube for my telephoto lens. (70-200mm Canon) I have an opportunity to purchase a number of macro tubes. Will those also work with the telephoto lens?

Answer

Yup, they'll work - tubes should work* with any lens, even a reversed one for extreme macro.

But the magnification is relative to the focal length - so adding 50mm of extension tubes to 200mm doesn't get you super close, show stopping macro shots. Using it at the 70mm end will produce higher magnification shots (although probably not 1:1), but less working distance.

Also, check out How can I estimate the reproduction ratio of an unknown macro setup? and How can I calculate the change an extension tube makes to the maximum magnfication of a lens?

*_{Obviously if they don't have electrical contacts you'll lose a lot of auto stuff, but that's not relevant to the focal length issue.}

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