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12-17-2010, 07:02 PM   #1
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So I got these lenses from ebay...

....they fit but they don't lock on my Pentax K-X

Am I boned or what can I do?
Minolta




Yashica



12-17-2010, 07:25 PM   #2
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Those aren't K mount lenses and never meant for Pentax cameras.
12-17-2010, 08:02 PM   #3
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The first is a Minolta MD mount and the second is a Yashica C/Y mount.
12-17-2010, 08:03 PM   #4
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you're out of luck with those. teh flange distance of minolta mount is shorter than the K mount, so there's no good adaptors out there that can make them work.

12-18-2010, 12:45 AM   #5
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Yashica-Contax C/Y-mount lenses can be easily modified to work on Pentax PK-mount cameras. The C/Y mod requires a Dremel; modded lenses will fit and can probably be made to lock on, but I haven't done that yet.

Minolta lenses cannot be used on Pentax cameras without MAJOR surgery. Have you a machine shop? Minolta MC-MD lenses can be used (with adapters) on m4/3 and NEX cameras. Yes, you are boned.
12-18-2010, 12:54 PM   #6
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QuoteOriginally posted by RioRico Quote
Yashica-Contax C/Y-mount lenses can be easily modified to work on Pentax PK-mount cameras. The C/Y mod requires a Dremel; modded lenses will fit and can probably be made to lock on, but I haven't done that yet.

Minolta lenses cannot be used on Pentax cameras without MAJOR surgery. Have you a machine shop? Minolta MC-MD lenses can be used (with adapters) on m4/3 and NEX cameras. Yes, you are boned.

What modifications can be made to make it lock so I don't have to hold the lenses in?
12-18-2010, 03:00 PM   #7
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Hi Edward,

If you want to go hunting on evilbay for glass to put on a Pentax body, target K mount and M42 mount glass. These mounts can be used directly on the Pentax bodies or through a simple adapter (K to M42 - available from Pentax). Here is quite an extensive list of lenses available that are available - note - just keep scrolling down......

12-18-2010, 08:42 PM   #8
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I'm not sure you realize that there can be more to having a fully functional lens than merely "locking on." Even in cases where you can physically adapt lenses, you don't necessarily achieve coupling for the various controls. Frankly k-mount lenses equivalent to the type you've acquired in other mounts are very inexpensive, to the point that you would be better off just starting with the proper lenses, unless you enjoy modifying lenses for a hobby.

Paul

12-18-2010, 09:15 PM   #9
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QuoteOriginally posted by clockwork247 Quote
you're out of luck with those. teh flange distance of minolta mount is shorter than the K mount, so there's no good adaptors out there that can make them work.
QuoteOriginally posted by RioRico Quote
Yashica-Contax C/Y-mount lenses can be easily modified to work on Pentax PK-mount cameras. The C/Y mod requires a Dremel; modded lenses will fit and can probably be made to lock on, but I haven't done that yet.

Minolta lenses cannot be used on Pentax cameras without MAJOR surgery. Have you a machine shop? Minolta MC-MD lenses can be used (with adapters) on m4/3 and NEX cameras. Yes, you are boned.
Actually, there are optical adapters for Minolta lenses to K mount cameras: eBay.ie: PIXCO Minolta MD Lens 2 Pentax Mount Adapter with Glass (item 190477298542 end time 06-Jan-11 08:14:15 GMT)

If it is worth the money is another matter.
12-18-2010, 11:09 PM   #10
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QuoteOriginally posted by Douglas_of_Sweden Quote
Actually, there are optical adapters for Minolta lenses to K mount cameras: eBay.ie: PIXCO Minolta MD Lens 2 Pentax Mount Adapter with Glass (item 190477298542 end time 06-Jan-11 08:14:15 GMT)

If it is worth the money is another matter.
True. Have a look at this thread (Minolta to Pentax K issue). Shame, theres tons of Minolta lenses on fleabay....
12-19-2010, 05:08 AM   #11
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QuoteOriginally posted by Edward_K Quote
What modifications can be made to make it lock so I don't have to hold the lenses in?
Place your C/Y lens face-down in front of you. Looking at the base, you will see three bayonet flags. One flag has a notch in it. That notch is near the "leading edge" of the flag. The problem is that the flags are too thick to fit under the PK mount lugs. The solution is to taper the undersides of those flags so that they DO fit under the lugs.
Definitions: UNDERSIDE OF FLAG: the side of the flag towards the front of the lens.
LEADING EDGE: the edge of a bayonet flag that first makes contact with a mount lug.
TAPER: Grind away the flag underside so its leading edge is wedge-shaped.
An Olympus OM-mount lens is similar; all three flags must be tapered. With a C/Y lens, don't taper the flag with the notch, just the other two. I use a Dremel metal-cutting disc to (CAREFULLY!) cut a slope that extends back about 8mm from the leading edge of each flag. The modified lens will now force-fit onto the PK mount -- good enough for careful use, but not locked on. A modded OM or C/Y lens should still be usable on its native mount.

Now comes the part I haven't done yet, but I should, on all the OM, C/Y and AI (Nikon) lenses I've modded. Force-fit the lens onto the PK mount. Note where the camera's locking pin touches the lens. Mark that point. Dismount the lens. With the Dremel, cut a notch in the lens base that will accommodate the locking pin -- about 2mm wide and deep, and 5mm long.

I didn't just devise this method out of thin air. I bought several cheap basic PK macro tube sets (US$7 shipped from Hong Kong). These have modular screw-on extension sections, and male and female camera-lens mount pieces. The female mount piece is an excellent test-bed for mount conversions. Loading a lens onto it is like looking at the lens from inside the camera -- you can easily see where bayonet flags and mount lugs do and don't interact.

Before modding a lens that means anything to you, I strongly recommend that you buy such tubes, and practice on a junk lens. This is really simple surgery, but it's still not for the faint-hearted. I am no machinist, oh no no. My mechanical abilities peaked when I was building slot-cars many decades ago, and I didn't even have a Dremel then. But proceed carefully and you should have no trouble. Be sure to air-bomb all metal dust away after cutting and grinding. Good luck!
12-19-2010, 05:20 AM   #12
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QuoteOriginally posted by Douglas_of_Sweden Quote
Actually, there are optical adapters for Minolta lenses to K mount cameras...
If it is worth the money is another matter.
And the problem with any optical adapter is that it degrades images a bit. IMHO using an optical adapter with a VERY SPECIAL lens makes the lens less special, removes some of the qualities that make it special. Also AFAIK most optical adapters act as teleconverters, increasing the effective focal length of the lens. So a magical Rokkor 50/1.2 becomes a pedestrian 75/1.8 or whatever -- not terrible, but not magical either.

And I am like totally bummed because I have some nice Minolta MC/MD glass I can't use and that isn't worth selling now. I think I've read that non-optical adapters allow their use on Sony NEX cameras, but I'm allergic to spending US$500+ on a new camera just to use a few lenses. Well, hopefully more NEX users will buy MC/MD lenses, driving prices up, so I can sell them next year.
12-19-2010, 06:55 PM   #13
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QuoteOriginally posted by RioRico Quote
And the problem with any optical adapter is that it degrades images a bit. IMHO using an optical adapter with a VERY SPECIAL lens makes the lens less special, removes some of the qualities that make it special. Also AFAIK most optical adapters act as teleconverters, increasing the effective focal length of the lens. So a magical Rokkor 50/1.2 becomes a pedestrian 75/1.8 or whatever -- not terrible, but not magical either.

And I am like totally bummed because I have some nice Minolta MC/MD glass I can't use and that isn't worth selling now. I think I've read that non-optical adapters allow their use on Sony NEX cameras, but I'm allergic to spending US$500+ on a new camera just to use a few lenses. Well, hopefully more NEX users will buy MC/MD lenses, driving prices up, so I can sell them next year.
I agree, which should be clear from what I wrote. I was only protesting against this statement: "Minolta lenses cannot be used on Pentax cameras without MAJOR surgery."

The exception is of course macro lenses, where you easilly can take out the glass from these adapters and get a simple non-optical adapter. You loose infinity, but who cares on a macro lens.
12-22-2010, 02:58 PM   #14
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Yeah. Though if the poster has to ask, he's unlikely to be doing mount adapting over a couple of old fifties in rough shape. Anyone got an extra A 50/2 on hand or something?
12-23-2010, 12:43 AM   #15
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As long as the seller provides an honest description of their lenses including the mount they've done the right thing and you have no grounds for complaint. Research the lens and mount compatability before you click the bid button.
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