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02-09-2014, 03:40 PM   #1
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Question about drill holes on Vivitar PK mounts

Hi,

These days I got a manual Vivitar 100mm Macro lens advertised as Pentax, which in truth turned out to be a Yashica/Contax lens. Since I paid next to nothing for it, I decided to keep it anyway, thinking that a fully reversible DIY conversion would be easy to accomplish. Unfortunately, this has not turned out to be the case.

I noticed that the drill holes on the Vivitar Y/C mount are totally mismatched when compared to other PK mounts like original Pentax PK, Sigma PK and Helios PK. But then it dawned on me that maybe if I get another Vivitar-branded PK mount lens I might be able to swap mounts between the Vivitars, since -- I am guessing -- the drill hole pattern should be the same for any Vivitar-branded mount.

Could anyone confirm or deny my suspicion?

Thanks in advance,
Guilherme.

02-09-2014, 04:21 PM   #2
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Could be....

Post a pic of the mount so we can see the screw positions.
02-09-2014, 04:53 PM   #3
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I would point out that Vivitar used a large number of suppliers for many of their lenses (the early series 1 were generally designed by Vivitar and then given to a selected manufacturer). The point is it may depend on the manufacturer and even then may change over time. Up to the 1990's generally the serial number begins w/ a code that identifies the manufacturer.

---------- Post added 02-09-14 at 05:00 PM ----------

If it was not clear from my post--Vivitar did not/does build lenses. Although they were on the forefront of designing lenses for a short time (e.g., close focusing fast zooms and fast primes, macro lenses, and mirror lenses)--perhaps the best known and still excellent is the close focusing series 1 70-210mm (versions 1,2,3).
02-09-2014, 05:08 PM   #4
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RioRico posted a simple modification that allows C/Y lenses to be used on K mount bodies.
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/144162-c-y-...ml#post1506028

02-09-2014, 09:47 PM   #5
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I've modified a Vivitar--a Kiron-made 28-85 f/2.8-3.8--from C/Y to K by using the mount from an old parts Pentax-A 50mm f/2.

Take the C/Y mount off, and then place the K mount over the end of the lens with its red dot lined up with the register mark on the lens. One of the screw holes in the K mount should align very closely with a screw hole in the lens base, so use that as one of your mounting holes. Then, using the C/Y mount as a template, drill two new screw holes in the K mount to match the other two C/Y mount holes.

I used the Pentax-A 50 mount because it turned out to be the same diameter as the old C/Y mount. An M mount might have been better (not having all the contact pin holes), but I didn't happen to have one available at the time. The diameter will probably vary with the lens you are modifying. I used a Dremel drill press, with all the adjusting screws tightened to minimize wobble, to drill and countersink the holes in the K mount.

The lens works perfectly on my Pentaxes, and if I ever want to get and use a Contax or Yashica SLR I can simply unscrew the K mount, reattach the auto aperture spring, and screw on the C/Y mount..
02-09-2014, 10:27 PM   #6
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Use double-stick cellophane tape to temporarily position the PK mount ring -- get it right as the adjustment for registration distance is often unique to the various mounting rings used on a common lens barrel. Then epoxy it and forget about hole alignment.

I've successfully done three "sex changes" that way with Minolta and Olympus lenses using scavenged PK bayonet rings. You may have to add a spacer too.
02-10-2014, 08:05 AM   #7
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QuoteOriginally posted by pacerr Quote
Use double-stick cellophane tape to temporarily position the PK mount ring -- get it right as the adjustment for registration distance is often unique to the various mounting rings used on a common lens barrel. Then epoxy it and forget about hole alignment.

I've successfully done three "sex changes" that way with Minolta and Olympus lenses using scavenged PK bayonet rings. You may have to add a spacer too.
Good idea about the tape. And yes, check to make sure the register distance provided by the two mounts is the same. On the Vivitar zoom I converted there was a spacer ring under the C/Y mount, and since the K mount was a little thicker than the C/Y mount, I left the spacer out when I installed the K mount. Register appears to be dead on, and infinity focus is sharp.
02-10-2014, 10:30 AM   #8
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elicar 90mm mount swap

On the same theme, any recommendations on "PK'ing" my elicar 90mm, currently minolta MD mount?

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02-10-2014, 10:39 AM   #9
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QuoteOriginally posted by marcusBMG Quote
On the same theme, any recommendations on "PK'ing" my elicar 90mm, currently minolta MD mount?
C/Y and OM are easy to convert because the focal flange distance is similar to PK. Minolta had a much shorter focal flange distance than Pentax. It would be better to find a PK Elicar and sell the MD to a MILC user.
02-10-2014, 10:55 AM   #10
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Macro lens conversions are good news/bad news. Infinity focus is not a priority, and you can even live with the effective short extension tube if the flange distance isn't perfect. The aperture can be annoying. You typically stop down to shoot, otherwise depth of field is almost zero. You have to either engineer a stop down lever or change the aperture ring while shooting. Focusing, metering and stopping down are really tough to do handheld when the aperture ring is the only way to stop down.
02-10-2014, 01:22 PM   #11
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QuoteOriginally posted by Just1MoreDave Quote
Focusing, metering and stopping down are really tough to do handheld when the aperture ring is the only way to stop down.
Yes thats a good point. The structure of this lens is such that I can't see an easy mod - your prompting sell it is the pragmatic way boriscleto.
04-07-2014, 08:58 AM   #12
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After a long absence, I can report back to say I had no success converting my Vivitar 100mm Macro from C/Y to PK. Unlike what happened to nparsons13, in my case an original PK mount did not fit the Vivitar perfectly -- it was a little bit too small. I spent an afternoon cutting hard plastic trying to make a flat O-ring which I could screw onto the Vivitar's back and then screw the PK mount on top of it, since the screws would not be in each other's way thanks to their being misaligned -- but that didn't work either. The good news is I could find a PK-mount Cosina 100m Macro with AF for under USD 50, so I'll probably be selling or giving away the Vivitar in the near future. Anyway, thanks for everyone's contributions -- they were much appreciated, even if I couldn't convert the lens.
04-07-2014, 09:39 AM   #13
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I also sold my MD mount elicar. I now have a vivitar version of the same lens in M42 mount - performance seems very similar. This is quite good because I now have plated brass* rimmed M42-PK adapters. The loss of infinity focus with these is relatively immaterial for macro shots, and the conducting nature of the mount means that the exposure compensations the lens asks for are "normal" ones, not silly maxing out +3ev ones. In fact I am moving to the opinion that these are better than the rimless ones (whether clones or Pentax) because:
1. all lenses are mounted tightly regardless of the width (spread) of the lens mount (narrow base lenses eg takumar 55's don't reach the camera mount so the tightness of the lens is only the tightness of the M42 adapter in the camera mount)
2. The adapter covers the camera mount contacts in all cases and corrects the exposure bollocks as already mentioned. I shall further note that by and large I do not seem to be experiencing mirror flopping with these.

These comments pertain to my K-r.

However I have a gripe about the viv: the A-M switch is small, a bit stiff and jammed between the camera mount and the aperture ring. Not easily manipulable at all.

*of the 2 I have purchased the better one was from seller ring.bow and is currently 3.92
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