Alley in Pisa, Italy

by Lars Kotthoff

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9
votes
1answer
286 views

What is the significance of the typical extension tube lengths?

I've been recently looking into getting an extension tube set for some macro photograpy. I've noticed that a lot of these 3 tube sets (for Canon EOS) have the same, very specific lengths: 13mm, 21mm, ...
23
votes
3answers
9k views

How can I calculate what the effect of an extension tube will be?

There must be a mathematical description of the difference that an extension tube makes to a lens -- is it something that can be easily described? (For example, with teleconverters you can say things ...