Contax V Leica Standard

[ZorkiKat]

I have two J-3. "White" barrels from 1953 (MMZ) and 1958 (KMZ). Both focus perfectly on Leica M, Leica LTM, and even my Epson R-D1s.

Does having a slightly different focal length affect the RF coupling and camming, when the lens barrel camming is made to accomodate that length? Were the Leitz 50mm (as well as the others from Canon and other non-Soviet 50 LTM RF lenses) exactly 50mm in focal length? I recall reading somewhere that the marked focal lengths were really nominal values at best- the real FLs were off by 1 or 2 mms.

Given that the Jupiter 50mm lenses did have slightly longer focal lengths, would it be right to readily assume that the soviet lens makers did not alter their barrels as well? It's always assumed that they did not- but what about assuming that they did? Without records or manufacturing descriptions, both remain assumptions. But wouldn't it be possible that they did it?

The soviets were first making FED Leica copies before they had Contaxes to duplicate. They were aware of what made Leicas tick, but the copies they made were not exact clones in terms of specs. They did follow the 28.8mm register after the war, as well as the standard flange thread English, instead of the metric, pitch.

Going back to the 52.5 (or even 53 or 55 in the case of some so-marked Industar 61 L/D) vs 50mm. Would it not be possible that the Soviets did adjust the camming of their 50mm barrel helixes to accomodate the 52.5mm length? In the same manner that they altered barrel helicoids for other focal lengths? If they knew how to do this for a 35, an 85, or a 135, would making on for a 52.5 be difficult?

The lenses I have come from the 1950s. That was a time when manufacturing quality was much better. I would tend to suspect that the faults are due more to manufacturing controls than the design of the lens itself, in cases of "NOS" lenses. Or else improper repair or "reconstituted" (one lens made of parts from several) assemblies could be blamed.

Jay

 

[Florian1234]

I voted for "other, good near, good far". As you might know, being pretty new to all that stuff, I'm not an expert. I use the Industar 26M lens which showed actually good results. I don't know if it is poor compared to other lenses, since I don't have the experience.
see my gallery for samples (partyl poor exposure).

 

[Stu W]

Jay has a good point. Why do my Leica lenses have their actual focal length engraved on them? Wasn't the dual range "special" as it's focal length was closer to the standard than other lenses?

 

[Santafecino]

Jay, Stu--
Here's the puzzle: As Brian says, the J3s and J8s have an actual focal length that corresponds to the Contax standard--and the helix makes no adjustment for the difference from the Leica standard. As he says, the link between the optical block and the focusing cam is a solid block of metal.

So the "50mm" lenses in fact aren't built like the 35mm or 85mm or 135mm lenses, whose cam duplicates the focusing range of a "standard" lens, but whose optical block obviously moves from near to far the appropriate distance for its focal length.
--Lindsay

 

[Santafecino]

Kim--
Put me down for a J9 LTM good far, poor near; a J3 LTM good far poor near.
Thanks,
--Lindsay

 

[ZorkiKat]

Jay, Stu--
Here's the puzzle: As Brian says, the J3s and J8s have an actual focal length that corresponds to the Contax standard--and the helix makes no adjustment for the difference from the Leica standard. As he says, the link between the optical block and the focusing cam is a solid block of metal.

So the "50mm" lenses in fact aren't built like the 35mm or 85mm or 135mm lenses, whose cam duplicates the focusing range of a "standard" lens, but whose optical block obviously moves from near to far the appropriate distance for its focal length.
--Lindsay

Lindsay,

The "puzzle" would lead to two more questions- and I am probably wrong about these assumptions:

One, if the barrel helicoids of a 50mm J-3 were to move the optical block to the necessary positions as required by a "true" 50mm to focus on various points, shimming the optical block to properly space a 52.5mm from the focal plane would not be the complete cure.

The 'focused' position (relative to the focal plane) of a lens with a length of 50mm aimed at say, 2 metres, would be slightly different to that of a 52.5 mm lens to focus at that same distance. Slightly different, but signficant enough to make focus discrepancies when large apertures are concerned.

Yet, as I would understand it, the general cure for many ailing J3 is to adjust the shims so that the optical block 'sits' at the right distance from the focal plane. And despite the theoretical concerns, Brian's fix seems to work.

The second is a personal one. Based on what has been said about how the J-3 or J-9 were made, my Jupiters should not be able work right on Leica or other non-FED/Zorki cameras at all. But they do. Another contradiction. 😀

Jay

 

[ath]

My Jupiter 8 is fine on my M2 for distant objects, but 2.5cm off at 1m.
Couldn't vote due to no tick mark for this.

 

[Santafecino]

Jay--
I've wondeed about that. If the only adjustment is to move the optical block out or in, the mismatch between the optics and the lens's cam (when mounted on a Leica) can't be cured. It can only be cured by slightly changing the focal length of the optics. That's what you're saying?

Another way of putting it is to say that, if you move the optics a bit and everything is sharp, there wasn't a mismatch problem at all.
--Lindsay

 

[ZorkiKat]

Jay--
I've wondeed about that. If the only adjustment is to move the optical block out or in, the mismatch between the optics and the lens's cam (when mounted on a Leica) can't be cured. It can only be cured by slightly changing the focal length of the optics. That's what you're saying?

Another way of putting it is to say that, if you move the optics a bit and everything is sharp, there wasn't a mismatch problem at all.
--Lindsay

Yes, Lindsay, that's exactly what I meant.

So if the fix only involves shims to reseat the optical block and the helixes move it to focus and couple with a non-Soviet LTM camera properly, then the Soviets have indeed reworked the J-3 LTM helicoids with the 52.5mm 'standard' in mind. If they did, then they did it right.

Jay

 

[Sonnar Brian]

And to really add to the confusion- there is the famous Sonnar Focus shift.

When I've shimmed J-3's, I set them to be sharp close-up and wide-open. At infinity, I tell people to use them at F2.8 or F4. Both the increase in DOF and the focus shift of the Sonnar lens being stopped down corrects the residual error.

The error when using a Contax lens on a Nikon RF is 1" back-focus at 36". The RF of the S2 indicates 36", and the actual focus is at 37". My solution was to move the internal helical of the S2 out a little bit and to recalibrate the RF. That way I could use my 8.5cm F2 and 13.5cm F3.5 made for the Contax on this Nikon S2. I've also shimmed two Contax lenses to work on a "normal" Nikon RF. The difference is the same as using a FSU lens on a screw mount camera calibrated for 51.6mm. The Nikon uses a "contax" bayonet that is calibrated for 51.6mm lenses. Put a Kiev Mount J-3 or a Contax mount Sonnar, and it will back-focus. Shim it, set the "sweet-spot" to wide-open and up-close, and use F4 at infinity. It just works. Nikon "did it right", their cameras focus with their lenses. And the focal length of their lenses work with Leica Screw Mount cameras. Nikon sold a lot of lenses in LTM. Some people might not like the way thay did it, too bad pass the beer nuts.

 

[Sonnar Brian]

They did. But if the mirror/focus screen/autofocus sensor EVER gets misaligned and the distances are not exactly the same as the light path to the film plane, it is very hard to fix. Been there, done that. No easily accessed adjustment screws. And you cannot easily compensate for focus shift for when the lens actually stops down. DOF Preview will help, but the screen gets dark and portions (microprism, Split image) can black-out.

 

[rxmd]

I've had alignment problems with exactly one SLR, and that was a Kiev 88 medium format SLR which has an easily adjustable focusing screen.

Philipp