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08-20-2014, 06:23 PM   #1
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Yashica DSB on Pentax K-50?

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So a friend was gifted two Yashica DSB lenses with Contax/Yashica mounts that he had no use for, and knowing the K mount admits many different old lenses, gave them to me. I found that the lens does fit inside the K mount snugly, it just doesn't rotate around and lock, as they have three separate levers and a weird bayonet. They are a DSB 135mm 2.8, a DSB 28mm 2.8 and a Kalimar 2x teleconverter for C/Y as well. I immediately looked around on eBay and found this:

Contax Yashica CY C Y Lens to Pentax K PK Mount Adapter with Optical Glass Cap | eBay

My question is: does this adapter work? I've tested both lenses with and without the teleconverter, and they work perfectly well (the 135mm is also better wide open than my Sears 2.8). They don't quite focus to infinity, however. The adapter says it allows infinity focusing, but it has an optical element, which means maybe quality will go down a bit? Also, how good are yashica lenses optically compared to SMC Pentax or other brands from those years? Build quality is superb, even though they're not in mint condition.

08-20-2014, 08:48 PM   #2
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A bit of history. Ashahi purchased the name Pentax from Zeiss. Also the original Pentax K 28/2 is a design copy of the Zeiss "Hollywood" lens, that Pentax received from Zeiss in a trade (rumored). There is also cooperation on the Pentax SMC and Zeiss T* coatings. Zeiss also helped with the K mount design - thus the C/Y mount incompatibilities. For what ever reason the two companies went their separate ways and Zeiss partnered with Yashica to build the Contax line of cameras and lenses. The C/Y mount is nearly a copy of the K mount with two important differences. 1) a very small difference in the registration distance, and 2) the thickness of the flanges on the mount. So, the lenses are not perfectly interchangeable, and no adapter is possible due to essentially the same registration distance.

So, no the adapter really will not work as I believe you intend it to, because it will set the lens too far away from the sensor (the registration distance). If these were Contax lenses, I would recommend the Leitax.com mount kit - remove the C/Y mount and replace it with a K mount. The parts run $100 per lens. This approach might not be cost effect for these lenses. Also, the Leitax mount kit is made for the tollarances of the Contax lens. The DSB mounts may vary in thickness from the Contax mounts.

What you could do is to shave the C/Y mounts. You would not want to do this to the Contax lens, since it would depreciate their value instantly. It probably does not matter so much for the DSB. So here is a post from RioRico - a legend here (who no longer posts due to his eyesight). But first - back to some history. The Pentax K and C/Y mounts are essentially the same - really both designed by Zeiss. However the C/Y adds a kicker by making the flanges a bit thicker so that the lenses would not be interchangeable. That is why you can't twist them on. Here is a shaving Rico's technique (I would suggest reading the entire thread).....I would also suggest buying a very cheap set of K mount extension tubes at about $10 or so. In this way you can mount the lens on the extension tubes and essentially see or view from the inside of the camera, as to what is going on the interior of the mount - another trick from Rico.
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from evil bay - the 135 goes for about $40 to $80 and the 28 goes for about $90 to $125.

Actually, the Yashicas are pretty decent lenses. Zeiss in teaching them to build the Contax line, transferred the knowledge to their Yachica line. The DSB's are the consumer line, with the ML being the premium line.


Last edited by interested_observer; 08-20-2014 at 09:00 PM.
11-10-2014, 12:10 AM   #3
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It's a shame that I'd have to physically alter these lenses; particularly the 28mm. I've looked around a little more and I've fiddled with the lenses for a bit longer now and it seems like the DSB's are cheaper versions of the Contax/Zeiss lenses, largely using the same optical designs. So far, from the highly unscientific tests I've made, the 135mm 2.8 DSB outperforms my Sears 135mm in almost every way: sharpness wide open, flare and ghosting control, CA, and image quality in general. I don't have a Pentax 28mm to compare the DSB against but apart from the missing infinity focus, it's an excellent lens and a keeper if it wasn't for the incompatibility.

Info is scarce about these cheap adapters going on on eBay, though. Does anyone have the C/Y to PK adapter, and if so, does it degrade the IQ enough for it to not be worth it? Most of the options available claim to fix the infinity focus problem with these lenses.
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