ssal

Anytime you can avoid putting another piece of glass in front of your lens, you should do that. If you're shooting with some expensive glass, no add-on is going to make the original better, only worse, just how much.

I prefer extension tube for my macro work. I have the very early version of Nikon rings which do not have any control. But in macro mode, I prefer manual focus so I can pin point the area I want to focus. I shoot aperture preferred, so the auto-exposure is right on. The dept control of with the extension tube is very effective.

Kenco makes some good extension tube set that is AF and AE compatible, but they are not cheap. For Canon, it is about US$150 for a set of 3.

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