PK lenses on PB Body?

[praktiman]

I know, I'm probably crazy, but I can't help it. I really love the PB bodies, esp. the BX20/~S.

The question is prompted by my recent reevaluation of my camera collection, which I'm considering divesting myself of in large part. This includes the Ricoh PK bodies. But I'm not fully decided on what lenses to keep, and which to sell on.

My Praktica bodies, I've decided to keep. This includes the PB bodies, which, as I've already mentioned, I'm very fond of. Most of you out there will probably say "That's crazy. You should do just the opposite: Keep the Ricohs and get rid of the Prakticas!" Perhaps you're right, but if forced to choose, I'd rather sacrifice the Ricohs. So please don't bother posting if that's all you have to say on the question.

Anyway, I have a SMC Pentax Soft 85/2.2. It occurred to me that since this is a manual aperture lens, with no diaphragm linkage to the body, mounting it on the BX20 might work. I've long known that the PB and PK mounts are to each other as the Exakta/Topcon mounts are, i.e. essentially identical, but with one being "rotated" relative the other. With a lens like the 85/2.2, it wouldn't really matter if I couldn't see the distance or aperture scales.

I went ahead and attached it to the BX. To my amazement, it mounted perfectly, even aligning "right side up" just as though it were a Prakticar. What I didn't expect, is that the PB mount flange is considerably thinner than the PK mount flange, such that the Pentax lens 'sags' on the PB body (i.e. the lugs on the lens mount want to latch onto something that is about 50% thicker than the flange on the BX20) and can be 'rocked' back and forth.

So, I'm wondering if anyone here has ever speculated on this question (or is willing to speculate with me now). Even if I decide to unload this lens, it seems to me it ought to be possible to "hack" this. Needless to say, the selection of lenses for the PB mount is limited, and if it were possible to make use of PK lenses, that would open a whole world of possibilities. I'm thinking that swapping a PK mount flange onto a Praktica body would probably be easier. My only concern is whether that extra mm or two projecting into the mirror box would interfere with the basic mechanics of the mirror/shutter sequence.

Anyway, I'll say again, I know I'm crazy. But these are the kind of things that make life fun for me. I'd really appreciate anyone's thoughts on how it might best be done (if possible).

Thanks in advance.

[philslizzy]

The mounts look almost exactly the same but they have a different mount and will NOT couple. I had the same problem.

[praktiman]

Hi, philslizzy. I don't know how carefully you read my post, but the mounts are not 100% incompatible. My SMC Pentax 85/2.2, which is a manual aperture lens (i.e. no aperture coupling hardware), mounts and locks on the BX20 body. The only problem is that the mount flange is not the same thickness, so the Pentax lens doesn't fit tight and flush. Instead, it sags, or hangs, at an angle of several degrees.

My question was whether anyone had ever tried to make a PK lens compatible by swapping a PB mount onto it, or make a PB body accept PL lenses by swapping a PK mount flange onto it. The PB cameras can still do AE in stop down mode, so the prospect of losing auto aperture function really doesn't bother me much.

Still interested in hearing people's thoughts. . . .

[iangreenhalgh1]

Forget it, Praktica B bodies are really crap compared to PK Pentax. I must have had 8 or 9 Praktica B cameras die on me, the electronics in them are often the culprit, I've had shutters break and wind-on mechanisms are weak too, had at least 3 break there. Pentax are light years ahead in build quality and especially electronics quality. Japan was leading the world in electronics in the 80s, East Germany was on the verge of collapse and electronics was one area where they were way behind the west.

The Praktica B mount and the Pentax K mount are almost identical, but they are not compatible and it is not a simple matter to make them compatible. The difference is in the thickness of the lugs, the lugs on Praktica B are thicker, so you would have to turn them down on a lathe to the right thickness. I suppose you could try to do it with a dremel and a grinding disk, but to me, that's just a good way to make a mess of it and destroy the value of the lens.

Secondly, the register is different, Pentacon Praktica lenses can have their infinity position adjusted, you have to take off the front nameplate and underneath are some screws which you have to loosen, then focus the lens to infinity, not infinity where it is marked on the lens, but by actually using an SLR and focusing on something a long way away, then re-tighten the screws.

All in all, it's a bad idea. Use Pentacon lenses with Prakticas and PK lenses with Pentaxes, Ricohs etc. Otherwise, you are going to have to do a load of machine work, which if you don't have the tools and skills, is a recipe for destroying the value of your lenses.

[iangreenhalgh1]

One other argument against using Praktica Bs is the tiny range of good lenses available. The Pentacons are very good, but there are only 2.8/28, 1.8/50, 2.4/50 and 2.8/135, that's it. The third party Prakticars are cheap nasty junk, the bottom of the barrel from Cosina, Sigma and Samyang, I've had most of them, all were crap. The only others are the rare Carl Zeiss Jena lenses, these are very hard to find and usually command pretty high prices because they are sought after, representing the final iteration of the CZJ lens line for 35mm. There are no long lenses (apart from a couple of very rare CZJ) for Praktica B and the only macro lens is a very rare Zeiss Tessar.

I kept the 2.8/28, 1.8/50, 2.4/50 and 2.8/135 Pentacons because they are very good and worth almost nothing so not worth selling. Sadly I don't have a working body for them anymore, I recently threw out two BX20s, a BCA and a B200 because they had broken.

[philslizzy]

[aoleg]

Would swapping the mount between PB and PK lenses work? Alternatively, there were M42 to PB adapters made. If you can attach such an adapter to a Pentax lens somehow, that would do the trick.

[Excalibur]

Well praktiman it's not only about liking a camera body, but also about what you can trust...I have a mint BC1 and just don't trust it after the "wind-on" jammed, to free it I attached the battery operated autowind. An intermittent fault is the worst (for anything) as you never know when it is going to happen.

[peterqd]

My thought: doctoring the lens to fit the PB camera is a bad idea because the (undoctored) lens is valuable, whereas the
camera is virtually worthless. If the camera mount can't be altered then use a PK camera. It wouldn't be wise to get rid of
the Ricohs just yet.