Quote Originally Posted by jstraw View Post
I'm sure this is something I shouldn't be confused about.

Here's an example. If I'm using an extension tube with a factor of 2.15 and a filter with a factor of 2.5 and I have an aperture of f4, id this the calculation or do I have this all wrong:

4 x 2.15 x 2.5 = 21.5(f22) and I adjust my shutter speed as though my aperture was f22 and then compensate for reciprocity as needed?
You use exposure factors this way with shutter speeds, not apertures.

If your shutter speed was 1 second, the new shutter speed would be 1 x 2.15 x 2.5= 5.375 seconds.

If you need to use them with apertures, you need to use the base 2 log of the factor instead.