As long as I'm getting answers to old questions, I'd like to ask our experts how Zeiss managed to make their 50mm Contax lenses all to rangefinder couple to the cam in the body, while Leica requires individual cams cut for each lens. Was the Zeiss manufacturing process so much more exact that they made every lens exactly the same focal length? I note that their other lenses (which mount on the external ring), all have individual cams just like a Leica (pun intended). Also, has anybody noticed the DOF marks on the Contax body are about two stops more generous than the Leica 50mm lenses. Were they just calculated for different COC, or did Zeiss think their lenses were that much better?

-- Bill Mitchell (bmitch@home.com), December 26, 2000

Answers

I am no expert but ... In case your faced with the question in a trivia pursuit game the "M" comes from the German word messen which means to measure. The Zeiss glass in the Contax IIa and similar vintage pieces may indeed have been better optically than concurrent Leica glass, but the 90mm baselength of the Contax rangefinder over the 73mm of the Leica III was probably more forgiving. Some "M" lenses won't work as well on the CL for these reasons. The achilles heel of the early Contax was it's shutter. The Leitz shutter today is still essentially the same design as the III. The design of M3 and forward to the M4 relied on hand finishing but also tight manufacturing tolerances. You can adjust the cant of the rangefinder coupling roller on a pre M4-2 body and correct for alignment error in the rangefinder patch. Cams wear like all metal surfaces.

-- Michael Johnson (mdjohnsonphoto@hotmail.com), December 26, 2000.

The old Contax cameras may have had a wider rangefinder base, but you ended up looking through a teeny tiny hole in the back of a fairly dingy finder for focusing. Depth of field scales are determined by what a manufacturer considers acceptable sharpness, so they can vary. I never heard of a lens having more depth of field than another of the same focal length. I guess a lens that resolves nearly 100 LPMM would have more acceptable sharpness on the fringe of depth of field than one that resolves 60 LPMM, but I'm not 100% certain of it.

-- Andrew Schank (aschank@flash.net), December 26, 2000.

Yes Bill, I am not clear here either. The later version Contax had the focus/ mounting ring/helicoid for the 50mm as permanent part of the body. This allowed for a smaller lens. What did you mean by "about two stops more generous"? Perhaps just having more physical space for engraving made this distinction possible.

-- Michael Johnson (mdjohnsonphoto@hotmail.com), December 26, 2000.

Marked hyperfocal distance of 16' is @f:16 for the Summicron, f:9 for the Sonnar. At f:16 the Sonnar hyperfocal distance is 11'. Focused at 12', the Summicron DOF @f:8 is 9-18' -- the Sonnar @f:8 is 7.5- 28'. It's like a free stop and a half, if you believe them. A 50mm LST Nikkor f:1.4 exactly matches the Summicron, while a 50mm Xenon on a Retina IIa is even more optimistic than the Zeiss (expained at least in part because the Xenon is actually a little shorter than the others).

-- Bill Mitchell (bmitch@home.com), December 26, 2000.

The Zeiss system didn't require more precision than Leitz. In both cases, the combination of lens and body has to be extremely precise. In the Leica, the focus helical is in the lens and the RF cam on the lens must be ground to perfectly match the lens focus. In the Contax, the focus mechanism is in the body and the lens cells must be positioned perfectly in the barrel to make the system work. In both cases, the design allowed for sufficient adjustment in the manufacturing process to correct for part-to-part variability in the glass.

The separate cams in the non-standard focal lengths are a mechanical necessity, as the focus travel of these lenses does not match that of the inner mount (similarly, non-standard Leica lenses use a ramped or articulated RF cam for this purpose, where the 50mm cam is just the flat rear face of the lens mount).

As far as differences in the DOF scale, I expect this was just the result of a different circle of confusion being selected as the standard for the scale, with Leitz being more strict. I doubt you'd see a difference in an image.

The superiority of Zeiss lenses in the prewar period came mainly from their use of complex cemented groups to minimize the number of air/glass surfaces, thus minimizing flare. With the arrival of antireflection coatings after the war, this became less of a benefit as Leitz lenses improved dramatically.

rick :)=

rick_oleson.tripod.com

-- Rick Oleson (rick_oleson@yahoo.com), December 27, 2000.

Subjective interpretation of objective criteria varies. Depth of Field Tables published in the 11/61 edition of Modern Photography give (General Photographic work) near point of 8',1.2" and far Point of 13',1.2" for a 50mm lens focused to 10' @ f/8. For Critical Work, the near point is 8',5" and the far point is 12',4". The writer notes: "The variety of depth-of-field tables engraved on lenses and on cameras, published by lens and camera manufacturers and appearing in countless guides and data sheets very greatly in consisitency and reliability. Many are hopelessly imprecise. ..." Using a circle of confusion 1/20mm or 1/30mm would give very different results than the accepted(?) 1/40mm for general photography or the 1/50mm for critical amateur or professional work.

-- Michael Johnson (mdjohnsonphoto@hotmail.com), December 27, 2000.

Okay, so the DOF marks are probably based on differing COC. Now back to the original question: Are the Contax 50mm lenses all manufactured or adjusted to the same focal length, or is there another mechanism in action here?

-- Bill Mitchell (bmitch@home.com), December 27, 2000.

Which 50mm? The sonnar for the I thru IIIa? The screw mount versions for the Leica? The latest designs? BTW, as noted above, lens coatings ultimately gave Leitz and others an optical advantage but the invention of coatings are attributed to Carl Zeiss. He apparently lost the control of the design rights inadvertantly. Most lenses including Leica's are a nominal rather than actual focal length and speed. Again circle of focus on the film plane like the COC is a relative measurement. My GUESS is that Zeiss designs have this tolerance as well.

-- Michael Johnson (mdjohnsonphoto@hotmail.com), December 27, 2000.

The Zeiss Sonnars could be adjusted in the barrel to bring the infinity focus to perfect register (I think they used shims, but I'd have to go back and look to be positive). Once this is done, the lens-to-lens variability isn't enough to cause problems at the closer distances. Kiev used a 50mm Jupiter and a 53mm Helios in the same Contax mount, with good success.

rick :)=

-- Rick Oleson (rick_oleson@yahoo.com), December 27, 2000.

Thanks Rick. Vellly interesssting. Humm, if it worked for Zeiss, wonder why Leitz cut their cams individually for each lens? Or did they?

-- Bill Mitchell (bmitch@home.com), December 27, 2000.

I will take a guess that it has to do with parallax correction being incorporated into viewfinder framelines in the Leitz designs. The roller follows the (cam shape) timing precisely and continuously thru the range for each lens. BTW the frameline's actual field of view changes from nearest point to infinity. This has a minor effect on metering in the M6.

-- Michael Johnson (mdjohnsonphoto@hotmail.com), December 27, 2000.

Good question, Bill. Just two my kopecks, please. The genuine focal length (the distance between the focal plane and the plane of max. sharpness) of any lens is not the same what is engraved on its front shield, but the same for the whole generation of lens and its formula. For example the focal length of any Sonnar 2/50 is about 52 mm (don’t remember the exact value). The acceptable error of focus length is about 0.005-0.01mm. Zeiss made every Sonnar the same focal length as well as Leitz made every RF Elmar, Summar, Summitar, Summarit, Summicron, Sunmmilux and the others its own, but also exactly identical focal length (depends on lens name/formula and version/generation) in limits of acceptable error. Only older Leicas (A, B, C) were matched to its Berek’s normal lens (Leitz Anastigmat, Elkan, Elmar) individually through the hole in the camera back. Shapes of Zeiss and Leitz lenses cams are designed in different way. Any Zeiss lens cam (for pre-M Leicas) has parallel working edge machining made, while most of Leitz lens cams are of more complex shape of declining working edge (on which marks of hand finishing are visible). It may be suggested that individual cams cut for each Leitz lens depending on its individual focal length. But its focal length is identical. So, it is right in that sense that working length of each cam is hand finished to match it to the identical lens focal length value because of summary error appearing inevitable during manufacturing process. M-lens cams are mostly machining made. As it is known the lens cams for LF-cameras are individually made for each lens, at least by Linhof. They buy lenses from Schneider, Zeiss, Rodenshtok without cams. Contax normal lenses are more small and simple in its design than Leitz’s ones. They have neither helicoid nor cam. Sonnar lenses 4.0/21, 2.8/35, 2/85, 1.5/85, 4.0/135 (which mount on the external lens seat) also have nor cams nor helicoids. The helicoid with the lens seat is in the camera body and simultaneously plays a role of the cam coupling to the lever of moving base of the RF prism. Was the Zeiss manufacturing process so much more exact that they? Seems, Zeiss had more advantages in that period. Famous Sonnar 1.5/50 was in producing from 1932, its coated version “T”– from 1935. But in 1932 Leitz from normal lenses had in producing only Elmar 3.5/50, Summar 2/50, (maybe Hector too) and Leica II, III. Bad coated Summitar was in producing only in 1939. Leitz Xenon 1.5/50 (Schneider’s formula) and then its analog Summarit appeared somewhere in early ‘50s. Sonnar’s formula by Dr. Ludwig Bertele is much better than Summar’s, the coating quality is also much better than Summitar’s. The RF-base of Contax is about 110 mm, screwmount Leica RF-base = 39mm. The quality of Zeiss lens is very high even today. I have and use a few ones for Leica. But then Leitz won the competition with his M3& Summicron. I dont’t know why the DOF marks on the Contax body are about two stops more generous than the Leica 50mm lenses. Maybe the genuine focal length of Summicron is a little more than Sonnar’s (?), somewhere about 54mm (?). But I did not meet exact value of any version of Summicron’s focal length.

Regars, Victor

-- Victor Randin (www.ved@enran.com.ua), December 28, 2000.

Wow! I'd say that answer is worth two Rubles, not just two Kopecs. Thanks!

-- Bill Mitchell (bmitch@home.com), December 28, 2000.

For what its worth, the DOF scales on my current Zeiss SLR lenses are calibrated one stop faster that those on my Leica M lenses and Nikon lenses. Zeiss has always used a different COC than Leica and Nikon. And yes, you WILL notice the difference. I always stop the Zeiss lenses down an extra stop when DOF is important.

-- Joe Buechler (jbuechler@toad.net), December 31, 2000.

CONTAX - LEICA comparing shutter accuracy on the "CLASSICS" as a year's project - M3 and earlier VS same units produced by Contax, over same time frame: I have tested shutter accuracy on these old clunkers, involving 23 Leica and 28 Contax and the results are a story of remarkable inconsistancy! In general ALL of the Leica units, ranging from Superfine ++++ condition to just working, had a MEAN shutter differential of 47% against the cameras settings, on the SLOW side while on a similar batch of Contax units the measurements are very much superior, producing a MEAN differential of only 18% - the ancient Leica shutter design of processed fabric are from the stone ages, at best incapable of precision lasting into the 70 - 45 years that have passed since they came out of the factory. The Contax units, with metal shutter blades fared much better. In the same way, the ancient lens design, materials and manufacturing methods of the era created optics that are what they are - from a pre-space age time, when all of the Leica/Contax 35's were at the leading edge of the very limited technology of yesterday. Lens testing over a range of product in the same shutter testing selections showed brutal results in terms of flare, abberations, resolution characteristics, and the like. Let's face it these are ancient cameras with out of sight prices bid up by collectors and not modern photographers. In modern terms the Contax C2 is a modern computer and the M6 is a typewriter. In actual use, an M3 in tip top condition, and with a variety of lenses, produce remarkable results - using B & W at ISO of 25 - get into modern film and that old baby is long in the tooth, incapable of being compared picture taking wise with a Nikon 60 (body at $300.00 or less.

-- Charles Lennox (charles-lennox@sympatico.ca), January 05, 2001.

Very interesting Charles. The incredible results some photographers attain with these old clunkers is a testament to their skill and the versatility of some modern materials. (Of course, some of the greatest writers still happily use their Parker 57s -- no computers, typewriters, or even BICs need apply).

-- Bill Mitchell (bmitch@home.com), January 05, 2001.

Subject: Leica vs. Contax lenses

Charles has given a comprehensive answer to the question but as Bill says it does not explain how such 'old' cameras can still give remarkable results. I have always believed, based upon what I have read and experience with Contax lenses, that this part of Contaxes was superiorto Leitz. The Contax shutters were not so reliable - mine failed - but according to Charles more accurate when working. On such opinions are our views based but the proof is in the pictures. People still use old Leicas and achieve remarkable results. How many Contaxes are still used daily ? I do see the occasional Leica III being used but I never see a Contax III. Am I wrong ? Where are you pre-war Contax users ?

-- Tony Brookes (gdz00@lineone.net), December 15, 2001.

There is a group of Contax rangefinder users:

Zeiss Ikon Collector Group

-- martntai@infinity.net (martin.tai@capcanada.com), December 15, 2001.

Interest in Contax RF is evident from the production of miniature Contax I

Miniature Contax I just like miniature Leica IIIf, M3

-- martin tai (martin.tai@capcanada.com), December 15, 2001.

Bill:

Looks like you got most of your answers, but this might be a useful addednda.

I THINK Contax used a very different "geometrical/mechanical" approach to the RF mechanism.

The Leica RF measures how FAR the lens is from the film, via the cam and roller connection. Each focal length has a cam to move the roller IN AND OUT a given distance between (say) infinity and 1 meter.

What I've read is that the Contax/Nikon RFs measure BARREL ROTATION to calculate lens position: i.e. ALL the various focal lengths ROTATE through 115 degrees (or whatever) to move from infinity to 1 meter. The lenses connect to the "50mm" focusing ring that is built into the camera, and it is geared (not cammed) directly and permanently to the RF mechanism.

RE: focal length variations. I thought Leica had 3-4 specific lens barrel/cam shapes for 50s, and chose among them based on the actually focal length measured after production - hence the little engraved numbers on the barrel (00, 10, 22, etc.) - rather than hand-shaping each and every cam.

Lens quality does not affect depth-of-field, per se - if anything, a crummy lens should have MORE apparent depth-of-field because the slightly OOF areas would be indistinguishable from the "sharpest" areas. Dianas have great depth-of-field because ALL parts of the picture are circles of confusion. 8^)

-- (apidens@denver.infi.net), December 17, 2001.

Contax G1 G2 are quite interesting.

However, I shall be quite excited if Contax can bring back a genuine manual focus rangefinder with modern Biogon, Sonnar, distagon, hologon...

-- martin tai (martin.tai@capcanada.com), December 17, 2001.

Martin, now that would really set the cat amongst us Leica pigeons here !

-- Mani Sitaraman (bindumani@pacific.net.sg), December 18, 2001.

[Wow, didn't realize this thread was still alive!]

Tony:

Another proud (pre & post-WWII) Contax user over here (Kyocera G2, too)! I think the main reason a lot fewer people use the old Contax RFs is that, unlike Leitz/Leica, Zeiss Ikon has been out of business for 30 years & there's no current product line to preserve interest in the brand & its heritage. [Incidentally, this relative lack of interest is 1 of the reasons why the Contax shutter gets a bad rap for reliability--there aren't too many around that have received proper maintenance over the years. The good side is that Contax bodies & lenses are much cheaper than Leica equivalents.] A lot of folks nowadays don't even know that Contax cameras existed before the Yashica/Kyocera models. Martin's right that the world would be a better place if Kyocera or another manufacturer would come out w/a high end manual RF system to give Leica some direct competition (perhaps not so good for the Leica co.)--after all, it was the rivalry between Leitz & Zeiss (& later Nikon & Canon) that inspired so many great RF innovations. It's too bad Nikon didn't decide to come out w/a modern M6-equivalent "S5" or "SP2" on the heels of the S3 commemorative.

-- Chris Chen (furcafe@cris.com), December 20, 2001.

Subject: Leica vs. Contax I just seen this statements from december 01 and would like to answer Tony: I use the CZJ Sonnar T* lenses 1,5/50, 2,0/85 and 4/135 in M 39 screwmount (made in wartime for export) with my M 4 P and I´m a great fan of that stuff. I prefer the Leica body for its quality and I do think that this old Zeiss lenses are as good (perhaps better) as the Summarits, Elmarits etc. Even the Summilux is matched by the f1,5 Sonnar. The Summicrons on the other side have a little more contrast especially for B+W. The old Contax cameras (pre- and postwar) were much more complicated then the Leicas and therefore not so reliable. I also think that prewar lenses as particular the Sonnars or the Summar combined with today cameras and films are best for stunning results, which you can not obtain with the SuperAchromatAPO-Lenses from today. Greetings

-- christoph wagner (diewagners@hotmail.com), February 20, 2002.

Not an snswer, but a big question: are Zeiss lenses for the Contax G2 better or worse than comparable Leitz lenses for the M6/7? And I don't mean just speed.

TIA, Mike Gregory

-- Michael Gregory (mgregory999@earthlink.net), June 27, 2002.