Backfocus calculator
Your reducer, your scope’s focal length, your camera and whatever goes in between: it tells you how many millimeters you’re missing and which spacers to use.
The result
What your frames measure overrides the manufacturer’s table. Below is the calculation from the table.
Calculating…
Then measure it with calipers and check it with a photo: the full guide, Backfocus, sin misterio, explains how (in Spanish for now).