Jump to content

Question About M2 Rangefinder with a Screw Fitted


Recommended Posts

Advertisement (gone after registration)

I've just tried an experiment where I fitted a screw 35mm lens to my M2, using a Voightlander screw to bayonet converter.

 

I noted the infinity mark on the lens was rotated slightly past the centre, (as if the lens had rotated slightly 'too far' in the mount) although the bayonet mount and the lens itself seemed correctly sited.

 

When I focussed on a distant object (about300ft) I noted the lens still had a little way to go, before infinity, when I moved the lens to infinity, the rangefinder image moved 'past' the object, although I would have expected them to have coincided at that range

 

Is this normal if you put a converted LTM lens on a bayonet camera, or should I proceed on the basis that the rangefinder is slightly off an needs CLA ?

Link to post
Share on other sites

Robert,

 

300ft might not be far enough to render a properly focused rangefinder image - try something at the horizon, or at least 1000ft away.

 

Did you try the lens on an LTM camera? Those have a much shorter rangefinder base and you might not see the discrepancy that you are describing.

 

If the lens' infinity mark screws past the 12 o'clock, the problem could also be with the adapter; if you have other adapters, check how those perform. Does the lens end up being positioned the same way on your LTM camera when screwed in all the way?

 

Good luck,

 

Jan

Link to post
Share on other sites

Hi,

Welcome to the club! :)

I've just tried an experiment where I fitted a screw 35mm lens to my M2, using a Voightlander screw to bayonet converter.

 

I noted the infinity mark on the lens was rotated slightly past the centre, (as if the lens had rotated slightly 'too far' in the mount) although the bayonet mount and the lens itself seemed correctly sited.

This is normal, as those lens are mounted on screw bodies. Position of "lying 8" about one o'clock.

 

Is this normal if you put a converted LTM lens on a bayonet camera, or should I proceed on the basis that the rangefinder is slightly off an needs CLA ?
This is NOT normal. But you should have the same effect with M lens too on this body then...

So it could be the lens (at best).

Link to post
Share on other sites

Jan

 

The fit appears to be the same on my LTM camera, with the datum mark slightly to the left of where you would expect it to be.

 

The adapter seems to be sited correctly and when I put on a VC lens that is 'straight' on the LTM body, it's also straight on the M2 body.

 

The lenses specifically that seem to have 'over rotated' are:

 

50 mm Summilux LTM screw

 

35mm Summicron LTM screw

 

I'm not sure whether this is a fault as such, it may just be an artifact - it may also be the case, as you say, that my 'target' is too close and the rangefinder is more accurate than I think !!

Link to post
Share on other sites

Here's one of the Summilux on my lllf Red Dial

 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Link to post
Share on other sites

As a quick update, the VC 50mm f2.5, which sits straight on both the lllf and the M2 also indicates the 'target' is slightly on the nearside of infinity - I'll check with a more distant object to see whether this is actually the rangefinder, or just a very, very accurate reading of distance !!

 

As far as the more recent screw lenses apparently 'over ratating' in the mount, I wonder if anyone else has noticed this... ?

 

Not in itself a problem, I'm just surprised no-one has noted this before

Link to post
Share on other sites

Here's the same lens on the M2, using the Voightlander 50mm adapter

 

Not a problem, I'm just interested if this is a common observation

 

Ps. The 35mm 'Cron does the same on both cameras too and comes from an unrelated batch.

 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Link to post
Share on other sites

Hello Robert:

 

I have a VC 35 COLOR SKOPAR which slightly over-shoots the mark (though not nearly as much as your lens seems to) and I have two other VC screw-mount lenses which don't quite get all the way to 12 o'clock. This seems to affect nothing.

 

Just informing you of my observation,

Robert Morrison, M4-P, etc.

Link to post
Share on other sites

Robert,

 

no worries. I have at least five original Leica screw mount to bayonet adapters, and they are all a little different. With some, my screw mount lenses overrotate a bit, with others they underrotate slightly, and with one or two of them the lenses sit at their "correct" position (or at least what we feel is correct). To make things worse, it also depends somewhat on the lens itself. Lenses I have tried are old screw mount Leica lenses, new Leica LTM lenses (the ones you have plus the 50mm Summicron) and VC LTM lenses.

 

Summarizing, you have to be lucky to find an adapter/lens combo that ends up sitting at the "correct" position. I have, however, never noted any problems with image sharpness that I could attribute to the adapters slight variations (although I have, as you have, noted slight discrepancies in the rangefinder image when using the LTM lenses on my M3 or M7). The base length of the M rangefinder is so large that even these slight variations can be noted (without any noticeable effect on sharpness though), but to tell you the truth, the same is true for new Leica M mount lenses. I have a variety of them, and on a given camera, say my M7, some of them (judging by the rangefinder image) slightly overfocus at infinity, some are spot on and others don't quite make it to the true infinity position in the rangefinder. On my M3 then, the latter ones reach inifinity, whereas the remaining lenses overfocus a bit more than on the M7.

 

To solve that "problem" you would have to exactly match every single lens to a given camera. It can be done, but as I said you are not likely to notice any effect except if you use the Noctilux, where things are crucial.

 

Cheers,

 

Andy

Link to post
Share on other sites

Andy and Robert

 

Thank you for your insightful comments - I tried a couple of quick experiments today using objects at extreme distance (width of the Bristol Channel, which is pretty extreme with the current weather conditions..!!) and it certainly looks like the 35 and the 50 both make the rangefinder focus slightly 'past' infinity, when the lens is correctly set to infinity.

 

I'm pretty certain the rangefinder is spot on.

 

I wonder if the amount of compensation needed matches the amount by which the datum mark on the lens is out of line with the corresponding point on the camera body.

 

I've tried a couple of tests by measuring camera to subject and comparing with the distance marks on the lens, and the greatest correlation is at the closer distances, with the over focus being more obvious at distnces of 12 feet and over, ie. rangefinder set correctly at a distance of 1m pretty much matches the 1m mark on the lens but rangefinder correctly aligned at 15 feet leaves the lens distance scale showing a fraction over 12 feet.

 

As said, I'm certain everything is working as intended, it's just an interesting artifact and I'll remember to give the lens just a little 'prod' when I'm using wide apetures on the Summilux beyond about 10 feet.

 

Look forward to posting some results soon !! :cool:

Link to post
Share on other sites

Don't get paranoid about 'over-rotation'. The adapter does its job properly as long as it provides the screw thread lens with its proper 28.8 mm flange-to-film distance, and also keys in the proper finder frames. Most RF lenses couple their focusing helicals to the rangefinder roller by way of a coupler that moves in a straight line back and forth, and this has lots of rotational leeway! So if the lens doesn't line up nicely, then the problem, if any, is just cosmetical.

 

The old man from the Age of Screw Threads on Everything

Link to post
Share on other sites

Robert,

 

My new-release 50 Summicron sits on both the iiif and iiig bodies exactly like yours at about 12:15 clock positition.

 

However, it does focus correctly and is perfectly focused at infinity.

 

Best,

 

Ray

Link to post
Share on other sites

Hello,

Back on this post, 35 & 50 screw mount do not stop at 12.00 but at 1.00 because in case you want to use an universal viewfinder VIOOH or VIDOM you cannot see the ranging and correct your paralax on the Uni. Viewfinder base if seat at 12.00.

Using lenses 73, 90, 105, 135, the extending barrel allow the user to see the focusing lines on the rotating ramp.

so when you screw this short lens 21 -> 50 on adapter rings you get the same 1.00 setting

Cheers

jc

Link to post
Share on other sites

Thanks Ray and Lars - JC That's a fascinating thought !!

 

I have checked using my lllf and lllg and both the rangefinder and focus seem to be spot on - interestingly, an older collapsible Summicron also roatates to '1 o'clock' so it sounds as thouigh you may well have the answer.

 

Where I am maybe a little more concerned is when the over - rotation occurs on a M series camera, using an adapter - the RF does seem to be off at infinity by a fraction and the amount of correction needed to make the lens markings match expectation (ie. so the 'lazy 8' aligns to the engraved line) is exactly the amount of rotation by which the lens has gone past the 12 o'clock...

 

Still haven't got a flim result to check but don't think the RF is off, as a VC lens which screws in to the adapter and aligns vertically at 12 o'clock is bang on....

Link to post
Share on other sites

  • 2 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...