LTM vs M mount optical differences?

brianentz · Mar 16, 2025

Recently I saw a video where someone compared two 35mm color skopar lenses on two camera bodies - one on an M mount Leica and one on a LTM Bessa. His results were that the LTM mount version of the lens had less contrast in parts of the scene.
I don't know why there should be any optical difference based on the mount of the same lens. Is it not more likely that any differences in such a contest were due to specifics of each lens apart from the mount? Perhaps one less just had more haze on internal elements? Or can the mount variance affect the design?

GregY · Mar 16, 2025

brianentz said:
Recently I saw a video where someone compared two 35mm color skopar lenses on two camera bodies - one on an M mount Leica and one on a LTM Bessa. His results were that the LTM mount version of the lens had less contrast in parts of the scene.
I don't know why there should be any optical difference based on the mount of the same lens. Is it not more likely that any differences in such a contest were due to specifics of each lens apart from the mount? Perhaps one less just had more haze on internal elements? Or can the mount variance affect the design?

Could be haze, there were also several series of the 35mm Color Skopar if i remember correctly but they only differed in the mounts...the optics were the same...7 elements 5 groups.
The one i had was sharp as a tack and modern in character.

Paul Howell · Mar 16, 2025

Or if contrast coatings, which have a long way in the past 60 years.

Focomatter · Mar 16, 2025

The optical difference between the mounts is 1mm. That is the thickness of the adapters. Leitz did this deliberately so that LTM lenses could be mounted on the new M3 when it was released. Therefore a better way to do the test is it shoot the same lens (with LTM mount) on both camera types. This negates lens to lens differences which is likely what the person found. I did not see the video. There could be other reasons relating to what happened with the film that was used.

mtnbkr · Mar 16, 2025

brianentz said:
Recently I saw a video where someone compared two 35mm color skopar lenses on two camera bodies - one on an M mount Leica and one on a LTM Bessa. His results were that the LTM mount version of the lens had less contrast in parts of the scene.
I don't know why there should be any optical difference based on the mount of the same lens. Is it not more likely that any differences in such a contest were due to specifics of each lens apart from the mount? Perhaps one less just had more haze on internal elements? Or can the mount variance affect the design?

The Bad Flashes video? If so, I watched the same one last night. FWIW, I have the LTM "Classic" 35 Color Skopar lens.
As with @GregY I suspect mild haze or something else subtle. IIRC, he did decide he liked the rendering of the LTM version better. The differences were pretty mild and I wouldn't reject the LTM lenses for the differences. If I had the LTM lens and acquired an M-mount camera, I'd use the LTM lens with adapter without giving it a second thought. I'd only consider it if I had the M-mount camera and was shopping for a 35 Color Skopar.

GregY said:
Could be haze, there were also several series of the 35mm Color Skopar if i remember correctly but they only differed in the mounts...the optics were the same...7 elements 5 groups.
The one i had was sharp as a tack and modern in character.

More than likely the case. Or just general wear, or some unpublished change in coating recipe as a result of manufacturing changes (similar to what we see in other consumer products).

Paul Howell said:
Or if contrast coatings, which have a long way in the past 60 years.

The video was testing two Voigtlander 35mm Color Skopar Lenses. The LTM was purchased used, but the M-mount one was purchased new. Ergo, there might be 20 years between the two, but anecdotally they use the same lens formula, coatings, etc.

Focomatter said:
The optical difference between the mounts is 1mm. That is the thickness of the adapters. Leitz did this deliberately so that LTM lenses could be mounted on the new M3 when it was released. Therefore a better way to do the test is it shoot the same lens (with LTM mount) on both camera types. This negates lens to lens differences which is likely what the person found. I did not see the video. There could be other reasons relating to what happened with the film that was used.

How is that a test between two lenses? He wasn't testing the cameras, but two versions of the same lens. But...doing what you suggest would rule out mount differences. That would require 3 shots: LTM, LTM w/adapter, and M-mount. Maybe that's what you meant and I'm dense.

Chris

chuckroast · Mar 16, 2025

I own both LTM Vogitlanders and newer Leica M mount lenses, but not the very latest of any.

On monochrome film, at least, I do not see dramatic differences. I will say that I've rejected Color-Skopars in the past because of in-lens haze due to the out gassing of the adhesives. This appears to be something that cannot be remedied, at least according to DAG for the lens I sent him.

Keep in mind that a native M mount lens of any kind is likely to be somewhat newer than the Voigtlander LTMs which likely means improved coatings and lens design.

As someone noted, you have to test the same lens on two different bodies via an LTM->M adapter ring to confirm it is not the body itself.

brianentz · Mar 17, 2025

mtnbkr said:
The Bad Flashes video? If so, I watched the same one last night. FWIW, I have the LTM "Classic" 35 Color Skopar lens.
As with @GregY I suspect mild haze or something else subtle. IIRC, he did decide he liked the rendering of the LTM version better. The differences were pretty mild and I wouldn't reject the LTM lenses for the differences. If I had the LTM lens and acquired an M-mount camera, I'd use the LTM lens with adapter without giving it a second thought. I'd only consider it if I had the M-mount camera and was shopping for a 35 Color Skopar.

More than likely the case. Or just general wear, or some unpublished change in coating recipe as a result of manufacturing changes (similar to what we see in other consumer products).

The video was testing two Voigtlander 35mm Color Skopar Lenses. The LTM was purchased used, but the M-mount one was purchased new. Ergo, there might be 20 years between the two, but anecdotally they use the same lens formula, coatings, etc.

How is that a test between two lenses? He wasn't testing the cameras, but two versions of the same lens. But...doing what you suggest would rule out mount differences. That would require 3 shots: LTM, LTM w/adapter, and M-mount. Maybe that's what you meant and I'm dense.

Chris

Yeah, that was it

Axelwik · Apr 28, 2025

Some used lenses are in excellent shape and others not so much. Other than the ravages of time and how they were used, treated, and stored there's probably not much difference between the two. Sure, in general original LTM lenses are older. A lens made for LTM in 1950 and one made for an M camera in 1954 has only a 6% difference in age - condition is king.

Get what you want, and if it's in reasonable condition don't fret about silly little differences and shoot some photos. That's what they're for.

LTM vs M mount optical differences?

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