How to mount an LTM Lens correctly ?

[jimbo035]

Advertisement (gone after registration)

Back as a user of a screw-mount Leica (after a 25 year gap), this time with a llf to lllf conversion and a Hove Collector Books reprint of the "Instructions for the use of Models c f & g" to  refresh my memory, I am a bit surprised that Changing Lenses (f section, page 31) does not say whether a lens should be set to its closest distance or not before being fitted to the camera.    

The downloaded copied Instructions I had for the Canon 7 (replaced by theLeica) clearly stated that only 'long' lenses should be set to their nearest distance, and this was not necessary for the short ones (e..g.35, 50mm) - or words to that effect.

I  found that when I fitted my Canon 50/1.2 set to its nearest distance to the Leica  the last turn or two were a bit stiff, but smooth as butter all the way when it is not.

Presumably this is also the Leica way ... but just in case I ever add a 90mm Elmar what's the rule for that ?

 

[spydrxx]

The rule I've followed for years is basically to mount LTM lenses at infinity...the infinity lock makes it easy to mount or dismount a lens, and one doesn't have to worry about a rear element on an ultra wide retrofocus lens protruding too far in the body cavity..

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[earleygallery]

The infinity lock makes it easier to change the lens - so it should be at infinity. Collapsable lenses should be extended when changing them to avoid damaging the focus cam or interior of the body. 

[pop]

.... one doesn't have to worry about a rear element on an ultra wide retrofocus lens protruding too far in the body cavity..

Should it ever protrude too far into the body cavity, it would do so at infinity. 

[250swb]

The 'rules' are there to stop clumsy people scratching an exposed rear element or scratching the interior blacking of the camera body. If you have a steady hand you can ignore the 'rule' and you'll probably find it rotates to infinity anyway as you screw it on, if not set the lens to infinity before mounting it.

 

Steve

[jc_braconi]

Start screwing with the infinity lock locked at 11 o'clock on the front flange

[willeica]

Advertisement (gone after registration)

I always mount LTM lenses with the infinity lock on and the lens fully extended and locked ie turned fully clockwise. This prevents any possibility that the lens might collapse while pointed straight or at an angle, thus possibly damaging a camera of any age or type. For mounting on a close up device such as the NOOKY or NOOKY-HESUM, the lens should first be collapsed and you should use the bayonet mounts on the collapsed central column to attach it to the close up device. Yes, a screwmount lens does have bayonet mounts on the central column, whose normal function is to lock the lens in its fully extended position and its use for close up devices is a good example of dual-function design by Leica engineers.

 

Finally, for those of you, with a masochistic streak like me, who might want to dismount and then remount a fixed Elmar on a Leica I Model A (say to inspect the shutter curtains or to clean the rear element,) ; first you must remove the infinity pin (carefully as it will be old and possibly bent) and then turn the lens anti clockwise. Note where the thread comes off the mount; this should be when the distance mark is pointing at about 1.25 meters on the circular distance scale on the camera lens mount. When you are remounting you should line up the distance mark on the lens with the 1.25 meter mark, or thereabouts, and turn clockwise. This should mean that the focussing knob and arm should end up at 11 O'Clock between the hockey stick clip and the infinity pin when the lens is fully screwed in. For feet scale lenses with close focus and thus an extra long thread you should follow the same practice. I cannot remember the distance number, but I did this successfully recently with my close focus I Model A. Practice makes perfect, of course.

 

William

Edited March 23, 2016 by willeica

[lleo]

I've never had any problem switching from a lens to another on my camera. They all get in the thread like butter.

Though the Voigtländer it's a little difficult, but I'll write it in the right thread.

[giordano]

The reason for the advice to set "long" lenses to their closest distance before mounting/unmounting no doubt relates to the rangefinder coupling.

 

On almost all "short" and many "long" lenses, the roller in the body rides on the ring-shaped cam just inside the lens mount thread (e.g. 5cm Elmar, Summar, Summitar, Summicron and also the 9cm Elmar. But on some "long" ones the cam is deep inside the lens mount and there is a relay rod with a "shoe" at the lens mount end to engage the roller. If the lens is focussed at or near infinity and screwed in or unscrewed in a hurry, the rangefinder roller gets pushed back with a jerk as the angled end of the "shoe" hits it. Such lenses include the 135mm Hektor and Elmar and the 90mm Elmarit and Summicron.

[Michael Geschlecht]

Hello John,

 

Thank you.

 

That is an important observation.

 

A bayonet mount 135mm  Tele-Elmar also has a shoe. 

 

Best Regards,

 

Michael

[Michael Geschlecht]

Hello Everybody,

 

Another observation: The "shoe" of a 135mm Tele-Elmar that contacts the "roller" is tapered on either side so that regardless of which direction you approach the "roller" from: The "roller" will glide up to the top of the "shoe" more gently.

 

Best Regards,

 

Michael