Non Leica 35 mm?

[caugustin]

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@aesop: No, no, shorter focussing distance has nothing to do with the overall optical quality of the lens. Or only a bit, because the lens has to be better corrected for the shorter distance.

 

There's this interesting fact that most 75 mm M lenses (Leica and other) have 1 m (or sometimes 0.9 m, as far as I remember) as their shortest distance instead of the technically possible 0.7 m. The only 75 I know to have 0.7 m is the actual Summicron-M 2/75 mm (I'd wish the CV 2.5/75 mm would have this). The 1 m is mostly claimed to be for the optical quality (correction), but I'm not so sure (perhaps back-focussing issues?), because for SLR/DSLR the shortest focussing distance is always much shorter than for M lenses. Same with 90 mm (the Macro Elmar-M being the only exception I know of).

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[Xmas]

@aesop: No, no, shorter focussing distance has nothing to do with the overall optical quality of the lens. Or only a bit, because the lens has to be better corrected for the shorter distance.

 

There's this interesting fact that most 75 mm M lenses (Leica and other) have 1 m (or sometimes 0.9 m, as far as I remember) as their shortest distance instead of the technically possible 0.7 m. The only 75 I know to have 0.7 m is the actual Summicron-M 2/75 mm (I'd wish the CV 2.5/75 mm would have this). The 1 m is mostly claimed to be for the optical quality (correction), but I'm not so sure (perhaps back-focussing issues?), because for SLR/DSLR the shortest focussing distance is always much shorter than for M lenses. Same with 90 mm (the Macro Elmar-M being the only exception I know of).

Hi

 

A significant factor is the helicoids for the lens optics and for the rangefinder follower would need to have a longer travel, and would be heavier. If you wanted more uniform performance at 0.7m and infinity that would need a floating element and yet another helicoid. A longer focus lens have to travel further to focus at 0.7m, than wide angles or normal lenses. The SLR lenses don't need two helicoids.

 

Noel

[caugustin]

@Xmas: Thanks for this! But SLR lenses didn't have floating elements in the past to give less focussing distance (so perhaps they had less optical quality at near focussing and the manufacturer did not care). But the second helicoid and longer travel are good arguments, at least for longer focal lenghts (but the 75 cron can do it, why not other lenses?).

[kanzlr]

while technically not a 35mm lens, the 40/2 Rokkor is close and a great lens.

 

Actually it feels pretty good using it

[Xmas]

@Xmas: Thanks for this! But SLR lenses didn't have floating elements in the past to give less focussing distance (so perhaps they had less optical quality at near focussing and the manufacturer did not care). But the second helicoid and longer travel are good arguments, at least for longer focal lenghts (but the 75 cron can do it, why not other lenses?).

Some of the olympus OM (SLR) lenses did have floating elements in '70s, e.g. the 28mm f/2 and 50mm f/3.5 macro, floating elements needed advances in element location provided by zoom lens technology developments before they were practical.

The cron would be lighter if it only went to 1m, the Russian 135mm f/4 in LTM only goes to 2.5 meters, it is really light, and small.

Noel

[caugustin]

Thank Xmas! This makes some things clear (i.e. why the CV 2.5/75 mm is a rather small and lightweight lense). Though Leica did a good job with the Summicron-M 2/75mm Asph. – it may be heavy, but it is rather compact, and an interesting item with its build-in hood.

[peter_n]

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There's this interesting fact that most 75 mm M lenses (Leica and other) have 1 m (or sometimes 0.9 m, as far as I remember) as their shortest distance instead of the technically possible 0.7 m. The only 75 I know to have 0.7 m is the actual Summicron-M 2/75 mm (I'd wish the CV 2.5/75 mm would have this).

Good that you point this out. The 75/2 is the perfect lens for tight portraits because of the 0.7M closest focus and its floating element that comes into play at that distance.

 

Though Leica did a good job with the Summicron-M 2/75mm Asph. – it may be heavy, but it is rather compact, and an interesting item with its build-in hood.

The built-in hood is unusual for Leica - it actually works! Why? It locks - what a concept!

 

By the way your English is excellent!

[thomasw_]

I own two different 35s. First a wonderful BP summicron asph that is well known and needs no further introduction. Secondly, I own a S-mount 2005 re-issue of the W-Nikkor 35/1,8 that came with a NIkon SP-2005 kit I bought. The lens is soooo tiny and such a solid performer throughout the apertures. I am going to get it converted to M-mount like this guy did. Admittedly the lens and the conversion are expensive....but I think it is worth every penny, and I look forward to mounting it on my M2!

[Xmas]

I own two different 35s. First a wonderful BP summicron asph that is well known and needs no further introduction. Secondly, I own a S-mount 2005 re-issue of the W-Nikkor 35/1,8 that came with a NIkon SP-2005 kit I bought. The lens is soooo tiny and such a solid performer throughout the apertures. I am going to get it converted to M-mount like this guy did. Admittedly the lens and the conversion are expensive....but I think it is worth every penny, and I look forward to mounting it on my M2!

 

Simpler getting one of the original LTM mount W-Nikkor 35mmf/1.8 although they only made a few they can be found...

 

Then you will have two to compare.

 

Noel