How many extension tubes?

[Suomi]

I was wondering if there is a quick formula when using extension tubes. I have a 28-105 which does macro at a 2-to-1 level, and I have 36,20 and 12mm tubes. What would I need for 1-to-1 and what would I get if I used them all for one shot?

Thanks

 

[G.K.Jnr.]

It will depend on what focal length you have the lens set at Mark, an easy way to check magnifications etc is to focus on the digits on a ruler. If you are using an APS-C size sensor then if you can fill the frame width with 24mm of digits you have 1-1, if you can fill the frame width with 12mm of digits then you have 2-1 etc, etc.

If you are using a Full Frame sensor then filling the frame width with 36mm is 1-1, if you can fill the frame width with 18mm then that is 2-1 etc, etc.

That's the way I work it out.

George.

 

[Suomi]

Thanks George that is most helpful.