Contax 50mm f/1.7 AE/MM differences

I've worked on both AE and MM versions of this lens before but have never done a direct comparison of the two. Recently I had reason to work on one of each at the same time so was able to do some direct comparisons of their construction. I thought it was worth recording what I found.

The two samples I compared had serial numbers 6504056 (AE) and 7380543 (MM). The differences noted may not be the same for all AE or all MM lenses.

Plastic/metal

The lens uses metal components for the focusing helical, plastic for the internal block that includes the aperture mechanism and carries the lens elements and a mixture of metal and plastic parts for the focus and aperture controls and front cover and dress ring. This is mostly the same in both lens versions except the focus ring on the MM version is metal but plastic on the AE version. The AE version I had showed why this change was probably made - it had cracks in the plastic around the screws that attach the ring to the focusing mechanism. This had caused the focusing ring to become loose and allowed the focusing helical to separate - which is how I came to have the lens. I have seen some cracks like this before so is clearly a potential issue.

Focus guides

Lenses of this general construction usually have one or more guides that allow the focus helical to move back and forth but stopping it from rotating. If these guides, or the slots they move in, become worn, slop or backlash can appear in the focus mechanism. Many lenses have one of the guides split so that its width can be adjusted to take up any excess. The AE version didn't have a split guide while the MM version did.

The slot in the helical component was also different in cross section which means the guide only contacts the helical at the edges in the MM version. What difference this would make I don't know.

Lens mount

The construction of the lens mount is completely different on these two lenses but I think the mount changed before the MM lenses were introduced so this isn't a AE/MM difference as such. The mount, of course, works in exactly the same way but the parts and their assembly is different.

I guess the question has to be, if the differences are so small, why is one lens suited to MM mode cameras and the other not. There may be other differences between the aperture mechanisms that are not really visible. The small constructional differences I could see between the two assemblies were not worth mentioning but maybe they do have some significance. The basic operation of both look identical.

Edit: I have, of course, passed over the infamous 'ninja star' aperture shape of the AE lenses. This is minimal on the 50/1.7 but it is present and shows the shape of the aperture leaves on the two lenses are different.

Yasuhara T981

I've created a new website for the above camera. Nothing Contax related but there is some Yashica interest. You can find it at www.t981.co.uk https://sites.google.com/site/t981yasuhara/home.

Phenix variants

NOTE: Since writing this I have completely changed my view on who made these FX-3 variants. They were, I'm now sure, made by Phenix in China and not Cosina. In fact, there is no evidence, that I've ever seen, to support the theory that Cosina made FX-3 cameras at any time. There is plenty of evidence that Phenix did though.

I've been doing a bit of research into what other cameras, made by Cosina Phenix, were based on the same chassis as the FX-3 and, therefore, may share other parts and be useful as donors. Or perhaps may be alternatives to buy and use. What I have found is there were a number of similar cameras and quite a few were made with the Pentax K mount - the previously mentioned Centon K100 being one and others sold under the brands of Vivitar, Braun, Hikari, Promaster, Kenko, Phenix and probably a few more. (Note: not all cameras sold under these brand names were based on the same chassis). Some of these were also available with Nikon or Minolta MD lens mounts. Most are mechanical cameras using the same Copal shutter as the Yashica FX-3 or FX-3 Super 2000 though a few, including the Centon K100, seem to use an electronic Seiko shutter.

I recently acquired a Vivitar V3000 and a V3800N which are all but identical to a Yashica Super 2000 except they have a PK mount. The V3800N was given a face lift and uses a rear door straight off the Centon K100 complete with the rubber covers.

So there are many models that came from Cosina Phenix that share parts and features. All are quite basic and mostly very usable. With a choice of lens mounts available these are cheap ways of maybe trying out a lens without committing to a full system.

As a, sort of, proof of the compatibility of these cameras, I took three cameras I had, all of which had issues and none of which were really worth repairing in their own right, and built one camera from the three. Most of the operational parts (shutter, metering system and viewfinder) came from a Yashica FX-3 Super 2000 but the chassis of the camera was in poor condition with a lot of paint loss so I used a chassis from an original FX-3 and transferred the parts to that. I kept the original FX-3 film advance mechanism in the chassis. I then fitted top and bottom plates, rear door and rubber covers from a Centon K100. Here's the result fitted with a Contax 45mm f/2.8 pancake lens and custom made hood.

I removed the Centon name and model from the top plate as that's not what the camera is. 

I'm now thinking of doing a similar thing with a PK mount body as there's a few Pentax SMC lenses I've wanted to try.