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10-22-2011, 06:01 PM   #1
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Konica-mount Vivitar conversion?

In a different thread it was stated that someone here converted a Vivitar lens from a Konica bayonet mount to a Pentax K mount. Aforementioned someone, are you still here?

I've found a Vivitar 20mm/f3.8 lens but it has the Konica mount. Eric's unsure about working on it but if someone here has gone through it I'd be very interested in the details, please. Many thanks!

Brad

10-22-2011, 06:29 PM   #2
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The film-to-flange distance for the Konica AR mount is 40.5mm, whereas it is 45.5mm for Pentax K. To make this work, you will have to move the lens optics 5mm closer to the film. This conversion can be done on long tele lenses, where there is a large distance between the rear element and the mount, but I doubt it would work for a wide lens like yours. You basically have to remove the mount, cut off 5mm, and reattach the mount. I have a Hexanon 40/1.8 that I would love to convert to K mount, but I don't think it's possible to do so and retain infinity focus.
10-22-2011, 06:39 PM   #3
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Some additional info that may help

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/56002-konica-m...onversion.html

vietlh81: How to convert Vivitar S1 70-210mm 2.8-4 Konica Mount to Pentax K mount
10-22-2011, 06:53 PM   #4
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Thanks! I would've thought that 3rd-party lenses would be designed so that nothing more than a mount change would be necessary, but perhaps that's only practical for the longer focal lengths.

Brad

10-22-2011, 07:13 PM   #5
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As you see, major surgery is required. (Any lens mod that employs a lathe is major surgery to me!) Lenses with universal adapter systems (T-mount, Adaptall, etc) are one thing, and they're easy; just get the right adapter. Lenses built for short-register systems like Konica are quite something else. Wide lenses especially are likely to have rear elements that would sit too far inside the Pentax body and foul the reflex mirror. Best bet for Konica lenses is to mount them on m4/3 or NEX cameras, with even shorter registers. Good luck!
10-24-2011, 02:58 AM   #6
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A couple of year ago I converted a Vivitar 55mm f/2.8 macro from Konica to Pentax mount, maintaining infinity focus and with a functioning aperture lever. As pointed out above this involved removing 5mm from the back of the lens + another 0.75mm for the flanged M42 to K mount adapter I fitted. This was done with a lathe which made the job a lot easier and quicker.
Vivitar like several other third party lens manufacturers make lenses for a variety of mounts. I believe that the basic lens is the same in each case with only the back end mount and aperture actuator being different for different mounts. For this reason there was enough clearance between the back of the lens / mechanism and the mirror to make the conversion possible. A photo of the conversion is reposted from https://www.pentaxforums.com/forums/lens-clubs/64271-impossible-lens-club-3.html bellow:

10-24-2011, 10:35 AM   #7
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I converted a Vivitar 28/2 from Konica to Pentax mount. I used the flanged M42 adapter like MattGunn.
I got around the registration distance difference because this lens has a very long focusing helicoid. I simply adjusted the infinity point and that was it.
Most lenses don't have that range of adjustment, unfortunately.
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