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01-14-2010, 04:05 AM   #1
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Pentax K-x and lens adapters

I understand the support that the K-x has for Pentax lenses new and old. My question concerns older SLR lenses from Nikon and Minolta, are there adapters to make it possible to use them on the K-x? I see people with 4/3 and m4/3 series cameras successfully using all sorts of old glass, and am wondering if it would be feasible to use the K-x in similar fashion, and what challenges using them would provide.

01-14-2010, 05:48 AM   #2
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QuoteOriginally posted by kpevav Quote
I understand the support that the K-x has for Pentax lenses new and old. My question concerns older SLR lenses from Nikon and Minolta, are there adapters to make it possible to use them on the K-x? I see people with 4/3 and m4/3 series cameras successfully using all sorts of old glass, and am wondering if it would be feasible to use the K-x in similar fashion, and what challenges using them would provide.
the biggest issue is what is called the regestry distance, specifically the distance from the mount to the sensor (or film)

minolta lenses have a lower regestry distance than pentax therefore any mount between the body and lens would need optical correction to achieve infinity focus.

Nikon, while having a slightly larger regestry distance does not allow sufficient space for an adaptor without loosing infinity focus.

There are adaptors for nikon to pentax, available from china, with optical correction, these have an approximate 1.25x magnification. I have one and it is potentially of interest for longer lenses but not wide angle.

the adaptors for 4/3 systems work because the 4/3 system regestry distance is so small there is room for a hollow tube type adaptor to mont SLR lenses
01-14-2010, 07:14 AM   #3
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Thanks for the explanation, it helps to actually know why things can or cannot be done.
01-14-2010, 08:19 AM   #4
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QuoteOriginally posted by kpevav Quote
Thanks for the explanation, it helps to actually know why things can or cannot be done.
Just so you are aware, there are forum members who are not afraid to get their hands a little dirty and have done conversions where they change the mount on the lens.

They usually use the "flanged type" M42 lens adaptor, which is a K mount with an internal 42mm thread to accept screw mounts. After market adaptors have a flange approximately 0.8mm thick, which can be screwed onto the lens in place of the existing mount, to convert it to K mount. This may require modification to some lens parts, but I have successfully done it on a kiron 28mm with Minolta MD mount, and been able to remove enough spacers, and surface grind one part of the lens, to still achieve infinity focus (even with the 2 mm shorter registration distance of the minolta lens)

My next project will be to do the same with a vivitar 24mm F2 that has a nikon mount. This will be easy because the regestry distance is actually longer so I won't have to surface grind any parts to make them thinner.


In all these conversions, you give up the automatic aperture but the lens functions in stop down mode and you can meter using Av mode, Focusing wide open then turning the aperture ring for exposure.

There are also posts with step by step for canon conversions as well but these are complicated.

01-14-2010, 01:10 PM   #5
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QuoteOriginally posted by Lowell Goudge Quote

Nikon, while having a slightly larger regestry distance
Some (myself included) have had success finessing a Nikon mount lens into a Pentax mount. The aperture setting window is off axis, but the lens mounts flush which is all that really matters. With minor modification I got my Nikon mount Sigma Filtermatic fisheye to mount snugly.
01-14-2010, 01:17 PM   #6
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while nikons can be "convinced to fit on pentax cameras, I prefer for perhaps an hour's work and about $6 for a flanged adaptor to convert them fully.

But that's just my opinion.

I know people have done it the other way too
01-14-2010, 01:18 PM   #7
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I admire those who can or will make alterations, but have to admit to not being one of those.
01-15-2010, 04:54 AM   #8
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The lens that work great and easy as manual lenses via adapter are my medium format Pentacon6 stuff, including things like a CJZ 180mm/2.8 Sonnar, all the Russian lenses deisgned to compliment the Kievs in P6 mount. Adapters around $25

08-24-2010, 09:10 AM   #9
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Hi can anyone help. can I fit minolta A-type lenses onto my Pentax K-X camera?

docmartin
08-24-2010, 09:13 AM   #10
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QuoteOriginally posted by docmartin Quote
Hi can anyone help. can I fit minolta A-type lenses onto my Pentax K-X camera?

docmartin
No. There is a chinese adapter for Minolta MD but not for Minolta/Sony A.
08-24-2010, 10:16 PM   #11
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I have castrated, er modded four Nikon and OM mount lenses to fit rather snugly on my K20D. My tools: screwdrivers, Dremel. My workshop: the wood railing on my back porch. The OM lens was a Vivitar and because of the way they built the mount, a flanged M42-PK adapter would not suffice, so I just trimmed a little material from the mount's bayonet flags. For the Nikons (one Nikkor, two Tokinas) I cut away the nub and arc at the bottom the the aperture ring.

I am no machinist. I hesitate at the prospect of grinding away at lens bodies to fix registry mis-matches. But I might dig out my grinding wheel and have-at the next Minolta lens that comes my way -- or maybe I'll start on some extra Leica-mount or Canon glass. It sure would be nice to mount the FD 50/1.4 SSC on my K20D, eh?
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