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02-10-2012, 11:39 AM   #1
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Suggestions on how to change a mount on a lens?

Hello All,

I've had awful luck trying to procure the right wide angle lens for my K1000. I've bought several, and they either end up broken or I end up taking a risk on a dodgy auction and getting something in the wrong mount. I've recently purchased a sigma super wide II on impulse without looking very closely, and now I'm sure it's not a k-mount. I'm a bit fed up and don't want to chalk this up as another loss. I'm wondering what it would take to remove the old mount and install a new one. I'm pretty sure the mount that's on this lens is one that adapters are not readily available for. I know the process will involve drilling holes in the metal to attach the mount. Any tips on this? Suggestions on places I could take it to have this done professionally? I have a k mount that I can spare, just need to know about drilling the holes. Thanks for any advice!

02-10-2012, 11:53 AM   #2
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It's not quite that easy. Different lens mounts have different flange focal distances.

Flange focal distance - Wikipedia, the free encyclopedia

You can replace the mount of a Leica R, or Contax/Yashica, or Olympus OM, but not a Minolta MD, or Canon FD. Nikon is close enough that it can usually be force fit with a minimum of modification for AI lenses.

Put up a picture of the Super Wide's mount and someone here will identify it.
02-10-2012, 11:55 AM   #3
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Would help to see pictures of your problematic lens(es).

I've modded a number of lenses to PK. Most NI, OM, C/Y, and Exakta (non-button) lenses are pretty straightforward. The only mount I've actually replaced is Petri Bayonet, and I may be able to replace a Pentacon Bayonet mount if I get off my moldy arse and Just Do It. But your Sigma probably isn't Petri nor Pentacon. If it's NI or OM or C/Y, it can be finessed. If it's Canon FD or EOS, or Minolta MD or Alpha, then the surgery just isn't worth doing.
02-10-2012, 12:16 PM   #4
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OK, thanks guys. I haven't yet received the lens, but here's a fairly vague pic of the mount from the listing. This may not help. If not, I will post better pics when it arrives.



it looked like a K mount at first, but now I'm noticing that notch on the right side in the metal lip, I have a Vivitar S1 70-210 with the same notch, and I think the mount is S/D or something like that? Not sure...

02-10-2012, 12:19 PM   #5
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QuoteOriginally posted by pentaxk1000denver Quote
OK, thanks guys. I haven't yet received the lens, but here's a fairly vague pic of the mount from the listing. This may not help. If not, I will post better pics when it arrives.



it looked like a K mount at first, but now I'm noticing that notch on the right side in the metal lip, I have a Vivitar S1 70-210 with the same notch, and I think the mount is S/D or something like that? Not sure...
It's a Minolta MD mount. Sorry.
02-10-2012, 12:23 PM   #6
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Maybe I should just buy a Minolta camera since I have this and the 70-210.
02-10-2012, 12:26 PM   #7
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Plenty of Minolta manual-focus cameras on shopgoodwill. Not much demand for the lenses since they aren't compatible with the auto-focus mount.
02-10-2012, 12:27 PM   #8
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I do not recall, on the minolta mount whether the aperture mechanism and lever are working in the same direction as pentax, so if you feel bold, and have either a scrap M42 lens that you can pinch the mount, or a flanged PK adaptor, you can remove the minolta mount and put the pentax flanged adaptor in its place, as long as you take care of any overhanging parts on the lens

you will be left with a lens that either needs infinity focus adjusted or you would need to machine the lens and / or adjust shims to correct the infinity focus due to the change in lens moount to focal plane distance between pentax and minolta.

if yuo are not afraid to try, you may learn something.

I have convertet kiron for minolta and kiron for nikon to PK lenses using a flanged adaptor and living with manual aperture.

the other issue though is that a sigma mini wide II is terrible for lateral CA so even if you suddessfully convert it, th elens is not really all that good.

there are optically compensated adaptors for almost every mount to PK now days as well but these are like little tele converters from 1.2 x to 1/4 x depending on maker and the mount types and distance needed to fit to a camera. they add their own problems as well as magnification, so unless you are stuck or are using it on a telephoto where the magnification probably does not hutr they are not worth using

02-10-2012, 01:09 PM   #9
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The lens is not that good? Huh, according to the reviews of it on this site, it's pretty good. The reason I've been looking for one is they go for about half what a K 24/2.8 goes for (or less) and it sounded like a good manual focus lens judging by those reviews. Maybe I should just bite the bullet and overspend on the K or A 24/2.8 I've yet to pay over $100 for a lens. I don't have a camera with aperture priority or auto anything, so I don't really care about auto aperture or any special features. I just want a good wide angle manual focus lens. I may mess around with it and see if I can fix it, or maybe I'll buy a Minolts SRT for $20 or so, or maybe I'll just try to sell it or stick it in a drawer and move on. Thanks for the input.
02-10-2012, 01:11 PM   #10
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Sorry to sound obtuse, but why are you having so much trouble? There are plenty of wide angle K mount lenses around, and all of them will fit the K1000.
02-10-2012, 01:13 PM   #11
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Unfortunately the MD expects to be 43.7mm from the sensor while the PK mount surface is 45.5mm away from the sensor. That means that the camera end of the lens must be shortened by 1.8mm.

If you are lucky, a flange type m42-PK adapter may be thin enough to simply replace the existing bayonet base (it was for me on a lucky occasion) - if not, the lens' base must be shaved somehow. You might see what's going on by removing the existing bayonet base; then hold the lens against the camera's PK mount & see if you can focus at infinity.
02-10-2012, 01:24 PM   #12
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QuoteOriginally posted by JohnX Quote
Sorry to sound obtuse, but why are you having so much trouble? There are plenty of wide angle K mount lenses around, and all of them will fit the K1000.
Exactly right. Best bet is to sell the MD Sigma to someone with a NEX, and buy a PK-mount wide-angle.
02-10-2012, 01:25 PM   #13
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QuoteOriginally posted by newarts Quote
Unfortunately the MD expects to be 43.7mm from the sensor while the PK mount surface is 45.5mm away from the sensor.
45.46, same as M42. C/Y is 45.5.
02-10-2012, 01:43 PM   #14
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Have you considered a Tamron Adaptall-2 24/2.5 (01B) with your choice of a PK or PK/A adapter? Max versatility. Quite satisfactory results IMO.

Tamron Adaptall-2 24mm F/2.5 Model 01B

https://www.pentaxforums.com/userreviews/tamron-adaptall-24mm-f-2-5-cw-24.html

H2
02-10-2012, 01:48 PM   #15
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QuoteOriginally posted by RioRico Quote
Exactly right. Best bet is to sell the MD Sigma to someone with a NEX, and buy a PK-mount wide-angle.
I know it seems easy enough to find a k-mount wide angle lens, and I've tried. For one, I don't want a cheap, low quality lens. I intend to buy something I can be happy with for some time. I've bought the following:

Vivitar (Kiron Made) 28mm f/2.0 - lens was essentially broken. The lens has a row of mini bearings that control the aperture lever, they were loose all inside the lens. Eric from pentaxs.com told me he wouldn't attempt trying to fix it and that it is not worth trying because of the bearings.

Vivitar (Tokina made) 24mm f/2.8 - Also somewhat broken. the lever that controls the light meter does not operate, so metering through the lens is not an option. I tried to take it apart to fix it, couldn't find the way to do it. The lens works, but I would like to be able to use my TTL meter. I wasn't overly impressed by the lens's performance either. Maybe that was due to my inexperience using it...

I think I just need to either be patient and wait for the right deal on the right lens, or stop being a cheap ass and pay the price for a K or A 24/2.8. $150 isn't a lot for a lens, I know this, but my frugality puts pressure on me to spend less. It seems like the popularity of quality k-mount glass has been increasing recently. Finding what I'm looking for for under $100 just doesn't seem as easy as I had hoped. :0)

pacerr - Thanks for the recommendation. I had looked at those once or twice, not a bad idea. I'll look into it more.
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