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90mm Elmar Focus Issue


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Hello All,

 

I am in possession of a LTM 90mm Elmar 1:4, SN 411XXX dating it to 1937. I'm finding that it has a focus inaccuracy which has been confirmed on several different bodies narrowing the problem to the lens itself. This is most apparent when the lens is focused to infinity at the stop; the lens markings line up where they should be at infinity, however the camera rangefinder shows a closer focus, as if it's telling you to continue rotating the lens to get to infinity focus. But of course I can't, because it's already at the infinity stop. Actual photo results using the lens show the camera rangefinders to be correct.

 

Is this a simple adjustment to correct and/or what are the options? Other than this issue, the focus and aperture actions are smooth, and the glass is excellent and it would be a shame to not make use of its potential. Thanks in advance!

Edited by cobbu2
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My 1939 Elmar 90 is perfect at infinity on my M9.

If in fact the lens is at fault (and it sounds like it is), the problem would be with the focus mount and not the shimming of the optical head.

Of course, a lens with that much history may have been cleaned and not assembled properly, possibly starting the focusing barrel one lead off. If you remove the lens from the M adapter you are using, and focus to the closest focus position, the focus cam should withdraw just about even with the end of the LTM mount. If it's an error in thread assembly that would likely be off.

The other slight possibility is the LTM-M adapter you are using, as I've seen some cheap ones with too thick a flange - but not that far off.

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If (as I seem to understand) the lens set at infinity does focus to infinty, but the Rangefinder does not coincide, the rangefinder cam is mispositioned... which can be occurred in occasion of some maintenance / cleaning; Elmars 9 cm are lenses of rather simple construction, and the issue can be solved by a good lab... with no great expense, but you must take into account that Elmars 9 are one of the most underrated classic Leitz lenses (that's the reason why I have 7 of them... ;)... is not costly, for a collector, to have all the variants or next to)

 

Just as a quick example, I have an item that is even older than yours (321.xxx) and here is a comparision with a much younger brother (1.355.xxx) of two crops, RF focused at around 2 meters, at f9 and f8 respectively (M8 unprocessed jpg)

321.xxx

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1.355.xxx

 

Of course , problem would be different if the lens also does not focus at infinity when set to...in this case can be that the optical cell is mispositioned : it is removable with a screw thread (that remained unchanged in all the variants, even in the last 3 elements version, and can be unscrewed to mount the lens unit on bellows / Viso) and can be shimmed to adjust the position of the optical cell.

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Thanks everyone for your fast replies!

 

Ok, I did some more experimentation. First, I see the same results through the rangefinder window using three different bodies, my M8 and M6 classic using a Leitz LTM adapter and with no adapter on my II (Model D) which has been CLA'd within the past year. To me, this rules out the bodies' respective rangefinder cams.

 

So on my M8, I mounted another lens and focused on a lamp post 25 feet away. I then re-mounted the 90 Elmar and turned the scale to 25 feet. The lamp post was in focus, but the viewfinder showed a split image.

 

I then focused on a cloud in the sky with the 90 Elmar at the infinity stop. The cloud was in focus but the image in the viewfinder was still split..

 

This tells me there is an issue with the lens focusing barrel. How is this resolved?

 

I agree Luigi, I think this lens is capable of outstanding results; all the more reason I'd like to solve this problem and put it to good use!

 

Once again, thanks everyone for your answers! :)

Edited by cobbu2
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As you turn the lens towards infinity, the Cam pushes the cam follower. Yours is not pushing far enough. You can build up the Cam using copper tape or something similar. The thin cam of the 9cm F4 Elmar makes it a bit more difficult. Sending it in to DAG or someone for adjustment is the proper way to repair it, but probably cost as much as the lens.

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Ok, I confirm that the problem is surely the RF cam... and try to check this measure, if you have a caliper :

 

This is the lens like yours, focused at infinity : the RF cam is the black ring that protrudes over the top : when lens is focused at minimum distance, it is completely rectracted, and not visible in such a picture :

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At infinity, the distance of the surface of the RF cam from the lens' flange ought to be 7,5 mm.

 

As I said, Elmar 9 is simple.. from what you said, I suppose that the above distance, in your item is something less... the cam moves "driven" by the focus ring but is a separate component , which can be badly remounted / positioned when the lens is disassembled. I suspect it's an easy repair... but no idea on how to fix it... in a similar case (on another lens) I "regained" the missing height adding two slices of scotch on the surface of the cam... very simple and rough way, which (by chance) proved succesful.

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Lenshacker and Luigi, you are both correct!

 

As it turns out, I happen to have a metric caliper and after measuring the cam distance at infinity, it's 1/2 mm short! It measures at 7mm even.

 

So... I can try the tape method, unless someone can show me how to fix this properly. I agree, I'm sure a professional repair will far exceed the purchase cost. It's also good to know the outstanding potential of this lens!

 

Thanks again!

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