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  ©luca vascon 2006

Contax Zeiss T* optics on Canon DSLR cameras, dream? truth?

 

Purposes of the test: to see if the Zeiss lenses were performing good on a digital camera, at least as good as a good zoom lens, and to realize if it is worth (for me) to buy a Canon dSLR with the idea of keeping it as digital body for the Contax system.

brief:
I've got a Contax slr, manual focus35mm system, that is the final solution of all my ancient speculations about usability, quality, and response to my specific needs. Now I need to go digital, for professional purpose, and my desire would be to keep my trusted and loved superb quality pieces of glass. But I also use and work, even digitally, with some Nikon lens, included the 8mm 2.8 AI Fisheye-Nikkor. I've experience in self building photographic hardware, and looking to the registry table of SLR systems, is clear EOS bayonet have the space to accomodate many other manufecturers' lenses, such as Olympus, Nikon, Contax, Leica R... without glass elements, allowing focus to infinite.

 Does it exist???
A symple ring allowing to mount other systems' lenses on an EOS digital reflex body,allowing focus to infinite... Yes, and more than one!

Market solutions:
Being Benatti out of market, the only other conversion ring serious manufacturer is Novoflex. They offer high quality solutions for Nikon and Leica lenses on EOS.
Two years ago I discovered, in a georgous mine of informations as well as beautyful site, cameraquest, a reference to a Yashica/Contax adaptor on EOS camera, here. It looks like to be VERY well machined etcetera, but a little pricy for my testing purposes. They also sell the widest range of adapter ever. However I can't speak of anything I have not tested, so I'll pass on. Also Fotodiox is offering a pro-version of this adapter, having experienced their Nikon adapter quality I think I'll buy one as soon as I've the money.

eBay solutions:
Obviously I looked forward a cheap source on eBay. I waited and found many. I have access to many DSLR cameras, so the only thing needed was the ring. I found many...



Contax/EOS adapter ring, no retain version.


the C/Y to EOS adapter, you can see the red C/Y lens coupling mark

from left to right: the EOS red coupling dot, the EOS lens locking hole and on the bayonet the useful stop screw, avoiding any damage if you twist the wrong side,

Lens retain or not?
When you mount a bayonet lens on your camera, you insert it and rotate till a familiar "click", than there is a button to release the lens. An adaptor, like a macro tube or a focal multiplyer, has to safelu click onto the camera as well onto the lens. You need the space, between lens and camera, to mount a retain system and a release button.
In case of Nikon and Leica adapters, no problem. For Contax lenses you can find the two versions...
Lens retain version
Since the space is poor, the lens retain version has no external release button. You mount the adapter on the lens, than you mount the lens on the camera.
Than you unmount the lens+adapter, and the adapter from the lens.
No retain version
In this case you can leave the ring on the camera, and unmount/mount the Zeiss lenses as you like. A flat spring in the inside of the bayonet, ensures a little strenght of retention. the lens needs to be tighten a bit, and you can focus or change apertures without unmounting the lens.
Does this work on all lenses? Well... my 28mm f2.0 fits a little bit loosy, as my 35 2.8 and a 50 1.7 MM. not enough to cause misalignment, but enough to take care not to unmount the lens while focusing! But a little screw allow to fine tune the spring.

Does it work?
It works. You can use it with some limitations:

Focusing: All is ok, but if you are used to have a stigmometer for correct focusing be aware. In the flat, clean field you will have neither the digital telemeter to help you! The 300d and the 350XT, "digital rebels" do not have a prism finder, but feature a mirror prism, so focusing begins to be complicated.

Beyond infinity: Infinity focus is guaranteed... but precision machinery is a costy thing. So they allow some tolerances, but they consider a thinner flange-to-flange adaption, that has the consequence that it allow your lens to focus OVER infinity. You will
never notice it if you do not usa a very wide lens: wides focus moving all optical elements of a very short distance, souch short that a 0.1 mm error can lead to misfocus. With fisheyes the thing becomes critical, and you NEED a PRO adapter ring.

Metering: It is stop-down mode. For me is the natural way of taking pictures. For someone else is not. However, EOS cameras can meter both in Aperture Priority and Manual mode.
exposition roblems were found with 1.4 lenses, 50 and 85mm have the tendence to overexpose of 1,6/2 stops. No try was done with a 35mm 1.4 Distagon.


 pictures of the lock release adaptor here.

  My test.
It was a test without any real scientific purpose: it involved a 300D, a 20D, a D1s mark2, as lenses it involved some of the most beautyful Contax ones (18 to 85) and 2 completely different Canon zooms, the 18-55 bundled with the 300D, a body-cap just grinded out of a Coke bottle... but surely not from a glass one, and the famous 24-70 f2.8, just taken out from the shelf. Some interior shot, on a tripod, some shot on the field.

 Considerations:
My final reply to the mai question is YES, I'll use my Contax lenses on Canon body. I can see no vignetting or aberration caused by light rays not being parallel to sensor, nothing in the 1.6x cameras nor in the 1x D1s markII, that shure has some workaroud for this issue, onboard. The expensive 24-70 is performing surprisingly good, even if is behind (for my taste) my Contax lenses.
On the opposite, the 18-55 given with the camera is so bad that a good consumer Powershot-A95 gives a far better result. Acceptable at 18, BAD at 55. It is a 100eur lens, in fact. Not more, not less... to be so cheap it is not so bad at the end.


Contax 45mm Tessar f2.8 on EOS 350D/Rebel-XT
here for the original jpg (2,5Mb!!!)
Tested cameras:
  • EOS 300D / digital Rebel
  • EOS 350D / digital Rebel XT*
  • EOS 20D
  • EOS 10D
  • EOS D1s MKII

*extensively tested/used, my own camera.

Tested lenses:
Carl Zeiss T* Contax/Yashica bayonet

18mm f4.0: excellent
25mm f2.8: excellent
28mm f2.0: a bit loose on the adapter
28mm f2.8: excellent.
35mm f2.8: a bit loose on the adapter
45mm f2.8: excellent, ultralight, ultrasmall
50mm f1.7: excellent
50mm f1.4: overexposed metering
85mm f1.4: overexposed metering
135mm f2.8: excellent.

Non-Contax lenses, C/Y bayonet

100mm f3.5 macro Yashica ML: excellent
200mm f2.8Angenieux 200mm f2.8: excellent