Hello,

I did a quick calculation of the bellows extension factor for my 210mm lens in a specific situation. I got:

210mm = approx. 8"
Length of bellows when focused on subject = 9"

(9/8)2 = 1.265

Log2 of 1.265 is about 0.37, which would be the difference in stops.

I know that's not a big difference and probably wouldn't matter in this case, but my question is, once the extension factor is calculated and the difference in stops is determined, do I increase or decrease the stops?

An easier example: if I'm currently at f/8 and I calculated the extension factor to be 2, which would mean a 1 stop difference, do I correct it to an f/11 or an f/5.6?

Thank you!