Question About LTM -> M Adapter

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chuckroast

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Is it the case that the LTM->M adapter you use only has to match the focal length of the LTM lens is there is a corresponding frame line set in the camera body.

That is, will any of these adapters work with any LTM lenses for purposes of focusing? For example, can I put a 28mm or 21mm LTM lens in a 90mm LTM->M adapter ring and still expect correct focus?

I'm thinking/guessing that the only difference between the various adapter rings is the position of the cams to engage the framelines in the body - which is irrelevant if there are no framelines for the lens in question - but that the dimensions of all the adapters are correct for engaging the focusing properly with any lens.
 
On well made adapters, this is true. On cheap adapters with incorrect thickness, you can typically use a 50mm lens as the movement of the cam is 1:1 with the optics. With wide-angle and long focal length lenses, the adapter thickness is critical to proper focus.
 
chuckroast said:
Is it the case that the LTM->M adapter you use only has to match the focal length of the LTM lens is there is a corresponding frame line set in the camera body.

That is, will any of these adapters work with any LTM lenses for purposes of focusing? For example, can I put a 28mm or 21mm LTM lens in a 90mm LTM->M adapter ring and still expect correct focus?

I'm thinking/guessing that the only difference between the various adapter rings is the position of the cams to engage the framelines in the body - which is irrelevant if there are no framelines for the lens in question - but that the dimensions of all the adapters are correct for engaging the focusing properly with any lens.
Click to expand...

In theory all SHOULD focus correctly, real world not all do.

LTM adapters can vary in

precision - some are thinner or thicker than specs, resulting in inaccurate focusing

position of the infinity index mark. Some aim for noon position. others are more like 10PM to view depth of field marking thru the viewfinder

some will mount on lenses with infinity locks - some won't.

some have cut outs for DIYS bar coding -- some don't.

some are all black, others all chrome
 
Sonnar Brian said:
On well made adapters, this is true. On cheap adapters with incorrect thickness, you can typically use a 50mm lens as the movement of the cam is 1:1 with the optics. With wide-angle and long focal length lenses, the adapter thickness is critical to proper focus.
Click to expand...
Never considered this! Fortunately my only cheepo adapter is my 50mm one
 
It's not just the frame lines, some LTM adapters interfere with the infinity focus lock on certain lenses. Some lenses will require a cutout in the adapter. The Head Bartender @CameraQuest has a handy page with examples of the different LTM adapter "types":
 
dourbalistar said:
It's not just the frame lines, some LTM adapters interfere with the infinity focus lock on certain lenses. Some lenses will require a cutout in the adapter. The Head Bartender @CameraQuest has a handy page with examples of the different LTM adapter "types":
Click to expand...

Is it reasonable to believe that sticking to actual Leica branded ones will provide reliable focus across all focal lengths?
 
Every correctly made adaptor should give accurate focus. Depending on the type some will give different frame lines but focus will be good. Some may not work with the digital M coding. Bad adaptors will be bad, most aren’t.
 
dourbalistar said:
It's not just the frame lines, some LTM adapters interfere with the infinity focus lock on certain lenses. Some lenses will require a cutout in the adapter
Click to expand...
This!!
There are lenses that cannot focus on wrong adapters because you cannot press the infinity lock down and and move the focusing ring.
 
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