View Full Version : 50mm f/2.8 Elmar adjustment
Has anyone had a LTM 50mm f/2.8 Elmar apart? I just bought one and although it's beautiful cosmetically, it front focuses by about 3 inches when I put it on my M9 or M8. Considering that it is incorrect on both bodies, and all of my other lenses are spot on, the Elmar is out of adjustment.
So, does anyone here know how to do it? I'm not afraid to attempt moving the optical cell myself, I've just never been inside a collapsible lens before. They are constructed a bit differently from the Rigid Summicrons, Summarons and all the Canon LTM's I'm used to.
Phil, do you have a different LTM to M adapter you can try?
The focusing error is far too great to be caused by the variation between LTM/M adapters. I tried the lens on 6 different adapters, all with the same result. The optical unit needs to be moved back probably half a millimeter or so.
The thickness of the LTM adapter is not the issue with a 50- the Cam and motion of the optics is 1:1.
Raid handed a unusable-glass 50/F2.8 Elmar to me for hacking purposes. I took out the optics cell, was not hard. Similar to the F3.5. I will look for it later, after getting home. Need to repeat it to write it up. Screw in the side of the lens comes out, think rear retaining ring but need to verify.
I just verified this:
1) Extend the lens fully.
2) Remove the single set screw in the barrel of the lens
3) remove retaining ring from rear.
4) Optics module drops out from the front. Easy to build up the point that the optics module rests, and then retighten with retaining ring. You will probably need to tap out a new hole for the set screw. Set screw required to hold the optics module in place with respect to aperture mark aligning near the center point.
I was wrong about the adjustment. Optics need to be moved back, not forward. Ouch. There's no room for adjustment on the barrel of the lens. Internally, there is the stop where the retaining ring holds the optical unit in place. At the end of the barrel where it meets the lip just inside the aperture ring, there is no room for back-adjustment either.
I see the "Front Focus" on the M8 and M9 now. I had some lenses back-focus on the M8, never front focus.
I had an Elmar 90/4 front focus on all of my cameras. I filed down the portion of the mount that the optics cell sits on. On a type 1 Rigid Summicron- bored out the fixture to replace the front element. New one was slightly wider.
Maybe possible to file down the inside of the mount, or to polish down the RF Cam.
Is your front focus really pronounced? Say, 2 inches? If so, then I'm leaving the lens as-is since it's really for using on a IIIf. I've got all sorts of properly collimated fun for the M9. Maybe I got ahead of myself and should wait to see what a roll of film delivers.
I've found that lenses which properly focus on a film camera can be that far off on my M8.
I would suggest trying it on the IIIf and adjusting it if off.
If you can, post some comparison shots here.
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