M8 behaves wierd with certain lenses

ampguy said:
To me, it seems very likely the OP picked up a couple bargain bin lenses that are slightly off. His M8 is probably perfect wrt mount and sensor distance.
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Sounds like a reasonable summary of the thread....
 
ampguy said:
do all 3 of your lenses behave the same with this simple test: http://nemeng.com/leica/024b.shtml ?
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I wouldn't trust the mirror thing too much. The camera body has a thickness, so when you focus on it, it will induce a slight mismatch to the "2" meters reading on the scale.

All three lenses does make the RF patch line up perfectly at infinity when they are set to their infinity stops. But only the Voigtländer actually reaches infinity.
The Voigtländer also focuses accurately at closer distances when wide open, but the other two focuses too close, which could be expected since they don't reach infinity.

My conclusion is that the CL lenses are calibrated for a slightly different film-to-flange distance. The only really wierd thing is the soft borders with the Summicron. I can't explain it at all. But, there is a little chans that this is "normal" when the lens is focused too close, and that it will be sharp across the field if calibrated correctly.
 
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Makten said:
Yes, I think so. It definitely reaches infinity wide open, even if the DOF is so deep that I don't know if it's sharpest a little closer to the camera. And since this lens also shifts focus, it's definitely at infinity at f/2.8.
On the other hand, the borders are quite unsharp. But I wouldn't expect them to be sharp when wide open at infinity.

The camera might have been dropped, because there is a tiny crack in the RF patch window on the front
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My conclusion is that the CL lenses are calibrated for a slightly different film-to-flange distance.
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My conclusion is: send the camera for repair, before investing in other lenses.

Makten said:
And please, let's cut the crap with CoC:s and all that. It doesn't belong in this discussion.
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Nice. What a waste of time.
 
ferider said:
My conclusion is: send the camera for repair, before investing in other lenses.
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Why repair something that's probably not broken? Hundreds of dollars down the drain. No thanks.
I'm not gonna invest in new lenses before I know that they work.
 
Alright, some news!

I just tried a Summicron 28/2 Asph, and it was sharp from corner to corner at f/2 and f/4. Didn't have the opportunity to try at infinity, but I think it tells me that there is nothing wrong with my camera. It also focused correctly at various distances (indoors).

So, while I'm waiting for the Zeiss Biogon, perhaps I should try to calibrate the 40/2 myself. I'm a laboratory engineer with decent knowledge in optics, so if I only know what to do, I can probably make it. I've partly disassebled lenses in the past to clean and lubricate them, and the problem is usually that there are no drawings, manuals, plans or anything on how they are built.

Any ideas? The whole inner assembly with the lens elements must obviously be moved a little bit while the focus helicoid should stay in the position it is.
 
The optical cell should be shimmed to the helicoid inside. You must replace the shims.
 
patrickjames said:
I will try to answer your question since everybody is either telling you crap about depth of field or telling you you are smoking crack for trying to use the lens on a M8. You have one of two problems as I see it. Hope for the first problem.

1-The entire lens assembly is shimmed wrong- Easy fix. It appears to have too much of a shim between the lens block and the helical mount. Remove the thinnest one. It needs to move only a very miniscule amount judging by your picture. It is possible too that there is something else (dirt, what have you) between the lens block and the helical mixed in with the shims. If you fix it this way for infinity and it is way off up close (focussing behind the object), go to #2 and say your prayers.

2-It is possible that someone put the lens back together wrong. If the rear elements are too far from the front elements (too much shim perhaps) it increases the focal length of the lens and will make infinity focus farther than it previously was. Another possibility is one of the elements could be off if it wasn't properly reassembled.

So hope for #1. If it is #2 it will probably have to go to a professional to get it fixed. At least you have a digital camera to check it on!

I am sure someone will point out some heinous error on my part in the above directions, but I am just trying to help.
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Thanks for a good answer! I'm gonna try the shimming, but my problem is that I have no clue of how to disassemble the lens: http://www.rangefinderforum.com/forums/showthread.php?t=85645
 
If I remember right you might want to trade your Leica 40mm lens for a M-Rokkor 40/2. As I remember the M-Rokkor 40/2 was made with a cam just like the rest of Leica line of lenses.
I have been using one on my M8 for just over 3 years and can a test to it being very sharp right out to the corners. I am using a 40.5-46 step-up ring, a 46mm B&W uv/ir filter and a 46mm screw in lens hood. The only gripe I have is I really do not want to trim the mount to another focal length so I just go on using the frame selector to 'guess' my framing.
 
I have Summicron-C 40mm and Elmar-C 90mm, both has focus spot on on my M8, actually C lenses has the same focusing cam like new Summarit-M 50mm.
 
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