Explain different frames on LTM to M adapters?

[ironringer]

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I am probably missing something basic, not owning an M (3, 2, etc.) camera.

Could users of Leica screwmount to M adapter rings, explain why some are marked with different frame lines that are activated for M2 compared to M3 cameras? For example, one adapter is marked M2 21-35 and M3 135. If the adapter ring basically acts like an M lens bayonet, that means this adapter (no matter what screwmount lens it holds) activates different frame lines depending on what camera it is mounted on. My conclusion is that the body mounts (bayonet cam sensors) of the M3 and M2 are different, so a given lens (or adapter ring) activates different frame lines on each camera. But that seems contrary to a "standard" mount for all M cameras, where a given lens should activate the same frame line on any M camera.

Does a 35 mm M lens activate a 35 mm frame on an M2, but a 135 mm frame on an M3?

Explanations are appreciated, thank you.

[250swb]

Well the first clue would be that the M2 doesn't have a 135mm frame, but the M3 does. This should explain everything to you.

 

Steve

[luigi bertolotti]

....Does a 35 mm M lens activate a 35 mm frame on an M2, but a 135 mm frame on an M3?

Explanations are appreciated, thank you.

 

A 35mm (AND/OR a 135mm lens) does activate A PAIR of frames : 35 AND 135mm : if the 135mm frame is absent (M2) there is nothing to activate, the same if the 35mm frame is absent (M3)

 

The couples are 35-135 28-90 50-75 and this is true for all the adaptors : simply, not all M cameras have the full set of frames (the first one with full-six-set was the M4-P)

 

The M8 has a little deviation thanks to its cropped format... 28-90 50-75 and 24-35.

 

The goggled 135 Elmarit does activate the 90mm frame which encompasses an image enlarged by the goggle unit, so that you frame anyway a 135mm angle of view.

 

The various goggled 35mm do activate the 50mm frame which encompasses an image reduced by the goggle unit, so that you frame anyway a 35mm angle of view.

 

It has never been clear to me why Leitz did engrave "21" together with "35" on the adapter... ... with 21 one must use the external Viewfinder... and can focus by RF with any adapter...

[spydrxx]

Also - just to clarify one of your questions...the mount for the M cameras is the same, in that they all accept M lenses or screwmount lenses in adapter rings. The rings are designed to bring up certain framelines (depending on the body as noted by others). But, you can mount any screwmount lens in any adapter...it just may not bring up the proper frameline, but it will focus just fine.

[ironringer]

Thank you gentlemen for your detailed and useful explanations of the M adapter rings and their frame line(s) activation, on the various M cameras.

[paorin]

It has never been clear to me why Leitz did engrave "21" together with "35" on the adapter... ... with 21 one must use the external Viewfinder... and can focus by RF with any adapter...

 

I think it means "for any lens with focal length between 21 and 35mm mounted on the M2". The other engraving with a range of focal lengths is M3 28-50, meaning "for any lenses with focal length between 28 and 50mm mounted on the M3".

 

As you say, with lenses <35mm on M2 you need an external finder and that adapter just brings up the 35mm frame line. So I guess the reason for Leitz to use those engravings was just to give the message to a non-expert customer that 21mm lenses can be mounted on the M2 instead of making him think that they are not compatible or he should look for another adapter.