People sometimes write and ask me how I test a given Leica lens + rangefinder combination for focus accuracy.
Well, for near distances I trust the good people at Vaseline.
On a related note, I dislike the grunt work of testing film equipment. The arduous process of developing and scanning film seems even more arduous when the test results are off. That is why I rarely sell gear that I know is working well (ha, ha…).
Fortunately, this time everything looks good.
↑ Leica M3, Leica 50mm Summilux ASPH, Kodak Tri-X 400, and Plustek 8200i.