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04-18-2012, 06:21 PM   #1
Anand
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Minolta 50mm f1.7 on Pentax K-x

I just bought a lens MINOLTA 50MM F1.7 MD MOUNT MANUAL FOCUS LENS (MPN: SMC-A50mmf/1.7) but I am not able to fit on Pentax K-x. Is there any adapter needed? or any other option?

04-18-2012, 06:28 PM   #2
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Short answer: Sell it. It is not compatible with Pentax cameras.

Long answer: I have a zillion lenses. I have modded various lens mounts to PK. I sold all my Minoltas because I'm not a skilled machinist and lens technician; and even if I were, modding Minolta-made lenses is nearly impossible. Because of design differences, a Minolta MD lens can never focus anywhere near infinity on a PK camera -- it's just another macro lens.

You CAN buy optical adapters -- probably for about as much as you paid for the lens. These act as short teleconverters, stretching and slowing the lens and hurting image quality. Your lens just isn't worth the effort. Sell it. Get a nice M50/1.7 instead, eh?
04-18-2012, 09:48 PM - 2 Likes   #3
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One member PM'd me a question based on the above. I'll post and answer it here:
QuoteQuote:
I read this answer of yours on the Visitor's center and it crossed my mind about using Reverse Rings. I have a Minolta lens on my old 7000 but I'm not sure if that can be used for macro. Is it possible for that Minolta lens on a reverse ring with a Pentax zoom for macro use? Thanks in advance!
The answer is NO, but not for the reason(s) you might think. Any lens (the SECONDARY) can be reverse-stacked onto a lens (the PRIMARY) mounted on a camera. But for decent performance, are some guidelines:

* The secondary should have an aperture ring. Whether Maxxum-Alpha lenses do is irrelevant. (I can't check that right now.) Pentax DA lenses certainly don't, and aren't suitable here.

* Both the primary and secondary should be primes. In my experience, all zooms used in reverse-stacking have terrible vignetting. The secondary should be shorter than the primary. Leave the primary's aperture wide-open, and control the exposure and DOF with the secondary's aperture. These are all necessary to avoid awful vignetting.

* The good news: Depth of the lenses' front insets don't really matter. At least, deep insets don't vignette. The magnification *may* be slightly affected; I'd have to test to be sure.

So if your Maxxum lens is a prime with an aperture ring, it *can* be reverse-stacked... onto a longer prime. Good luck!
04-20-2012, 04:20 AM   #4
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QuoteOriginally posted by Anand Quote
I just bought a lens MINOLTA 50MM F1.7 MD MOUNT MANUAL FOCUS LENS (MPN: SMC-A50mmf/1.7) but I am not able to fit on Pentax K-x. Is there any adapter needed? or any other option?
Judging from your question, I suppose you need the clarification that every camera company has its own lens mount, and that lenses are not supposed to fit a mount they were not designed for. [exceptions exist though, but they're not the case right here]. Next time you purchase a lens for your Pentax, make sure it has a "K mount".

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