Yashica Camera to Pentax Bayonet Mount

Posted on Posted in Camera, Photography, Projects

If there is anyone visiting my site that cringes at the desecration of high performance optics, you may want to look away now. My dad has long proposed taking one of his old lenses from the film era and converting it to be used on one of our digital cameras now. He had a pair of primes and a telephoto lens collecting dust, and I guess he wanted them to see some more use before they disappeared in a box somewhere. The problem with this is that every manufacturer has a different camera mount, which is why you can’t put a Canon lens on a Nikon camera without an adapter. For older lenses like Yashica/Contax, there may not be adapters. You would have to physically remove the metal locking ring and swap it with a compatible one. So that’s what I did.

There are a few people out there who will machine you a custom mount (ex. Pentax mount with compatible screw holes for a Yashica lens) but from browing online, that costs between 30 to 60… euros. Well, that’s unappealing. So I decided I would do my own transplant, a mount from an old Pentax 35-80 f/4-5.6 to a Yashica Prime 50mm f/1.9. That same European site from earlier however, includes some detailed instructions on mount conversions, complete with pictures! And so, I was set.

The hardest part of the entire ordeal was removing the original lens mount from the Yashica. Aside from using size #0 screws, the threads of the screws are apparently glued in. I did some preliminary tinkering with a cheaper Tamron 35-135mm Tele-Macro lens of the same era as the Yashica, but I stripped a screw almost immediately. I didn’t break the lens, but that did mean it would live out the remainder of its life un-upgradable. I moved on to my intended victim with no practice under my belt.

The Yashica Prime was slightly more yielding to my screwdriver. I managed to get the plastic matte ring off without a problem (prevents stray light from bouncing around the inside of your camera, messing up your pic), but when it came time to get the metal mounting ring off, I stripped 2 out of 4 screws. At this point, I was mad. I didn’t want to have to try this operation on my dad’s final Contax lens. So I took out the power drill and forcibly removed the screw heads. It wasn’t until now that I decided that a bit of scotch tape over the lens elements wouldn’t be a bad idea. Something about metal shavings flying around delicate glass finally registered in my head.


Once the mounting ring was off, I had to remove a thin perforated metal disk from the bottom of it. This disk, combined with a ball bearing, is what clicks when you turn the aperture ring. The ball bearing is falling into specific groves. That disk would stay with the original lens. It was time to match the Pentax mount (which came off without a fight) to the Yashica lens. The biggest problem here was that the screw holes did not match up. At all. I ended up drilling my own screw hole.

Since I only ever managed to pull out two intact screws from the Yashica, I could only use those two to secure my new lens mount. To maximize what little mechanical integrity I had available, I drilled my own screw hole opposite that of the one I had first chosen. The first screw hole was chosen, by the way, to ensure that “up” on the lens roughly matched “up” on the mount. Since the lens was now completely manual, I had to be able to read what I was setting it to (aperture and focus). I used a 9/64″ drill bit to recess the screw head, and a 3/32″ bit to finish the screw hole.

Everything must go!
When I finally put the Pentax mount on the lens and tried it on the camera, I got a little bit of resistance. It thought that maybe something was catching in the empty holes where electrical contacts used to be. I put those back in, to no avail. I looked again and realized that the mount had deformed. The plastic sleeves for the electrical contacts was too thick, vertically. So that had to go. With the mount now undistorted, it snapped into my test-camera perfectly. I took a test shot to compare the effects of aperture.


Basically, I have a lens from like… the 1970’s, that I converted to fit a modern DSLR. It’s a prime lens, which will help if I ever try to do night/star photography at night, or I ever want to take portraits or indoor photos where lighting sucks (read: dorms). It does render one lens useless (the Pentax I cannibalized), but that one was already obsolete. A kit 18-55 + a 55-200 we have lying around pretty much solve that, especially since APS-C cameras have an effective magnification anyways. An 18-55mm on an SLR turns it into a 27-82.5mm, compared to a 35mm camera. In my opinion, giving an old Prime some use is well worth the tinkering. Plus, manual controls build character. And experience. It will force me to move to get my shot, and make me appreciate everything my camera does to balance a shot, like shutter speed and ISO. What it won’t do, however, is keep me from drooling over Canon tech. Despite absolutely horrible reviews of the EOS 60D’s sensor quality compared to Pentax, Nikon, and Sony , Canon still has superior video features. Considering they make camcorders, you shouldn’t be surprised. But the fight between the Canon T3i/60D and Pentax K-5 for my wallet is best saved for another day. Alas, since I’m not really a legitimate review site, I can’t request evaluation models…

Full photo album available here: http://www.facebook.com/album.php?aid=2082195&id=1338510228&l=ccfeb0c783

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