35 f1.5
35 f1.5
Hi Hayden,
My example is every bit as sharp as the Nokton 40mm 1.4 (shooting the Nokton almost but not quite wide open to give f1.5 and the Canon wide open, both close up, both on the R-D1). I can't yet vouch for the far corner performance vs. the Nokton as I have not yet shot film with it.
When I got it was a bit soft wide open close up. So.... (warning: before going further, if you have worked on lenses before this is superfluous. but if not, be aware that you can mess up a very expensive piece of equipment. Work over a white towel --to catch the tiny screws--and work carefully and slowly and with a good set of precision screwdrivers. Be sure you understand how the lens is put together, and if something seems not right stop and do something else and ask someone on the forum about it).
First, check the length of the rangefinder cam on the lens against a 35-50mm lens you know to focus correctly. You can often do this by putting the two lenses back to back but offset to measure their cams against each other at infinity. Also check on a distant power-pole or tree that the lens truly brings the rangefinder to infinity (the images completely coincide). If the focus is off on the lens you will need to adjust the focus mount before getting started. My mount was off a little and did not bring the images to coincide fully.
Second, once satisfied that the focusing mount is okay you will need to determine whether best focus is in front or behind where it should be (there should be some threads here somewhere that can tell you how to figure this out). It quickly became clear that the optics of my lens were positioned a bit too far away from the sensor for a given distance on the rangefinder and tape measure. In other words, the shim on the lens optical block was a hair too thick. I then removed the shim and gently and carefully rubbed it against emery paper, reassembled, shot, dissassembled, etc., until rangefinder, tape measure and sharpness were all in synch.
Caution--if you remove too much you will have to fabricate a new shim (or try to get a local machine shop to do so)!
In my case I did the test on the R-D1 for convenience because I know it is spot on with several different lenses with one of my screw to m adapters. If in doubt, another way to do this is to mount the lens on a film body and tape a matte screen in the film gate (I keep an OM screen around for this purpose). Then put the rig on a tripod and examine the focus with a 10X or stronger loup.
All in all it is not hard, but it is a bit tedious. Also, I'm sure that if you don't want to risk it someone on the forum knows who you can send it to.
Hope this helps,
Charlie
PS: Warning: do not remove or disassemble the diaphram--these are a pain to reassemble.