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07-31-2009, 10:36 AM   #1
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infinity focus adjustment on M42 lenses

how easy is it to adjust infinity focus on takumars?

I only have a few M42 mounts, and you can get flanged adaptors on e-bay for $6 each or $60 for 10.

the flanged adaptors are meant to be perminantly attached to a lens as they have a locking pin location for the K mount,

the problem is, infinity focus on my 35mm F2 might be lost, therefore how can I re-adjust it?

for me it would be much easier to convert the M42's I have to K mounts as opposed to fussing with the adaptor, and I like the flange mounts because of the locking pin

Note this was initially posted in the Takuamr club, but another member thought it was worthy of it's own thread

07-31-2009, 11:34 AM   #2
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Difficulty, I don't know. I used to think it was hard, but after a little practice, it's easy.

I tried this out with an S-M-C Takumar 50mm f1.4 and a flanged adapter. There wasn't enough adjustment range for it to work. But in the thread I started about it, someone else said that it did work on the 35/2. I would hedge my bets and buy the thinner adapter.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/54595-flanged-...xperiment.html
07-31-2009, 12:27 PM   #3
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Great idea. It certainly is worth trying first.

If you can't find a thin flange, sand one down!
07-31-2009, 12:39 PM   #4
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I have stripped and rebuilt M42 takumar:
50 f/1.4
55 f/1.8
135 f/3.5
and can confirm that there is very little if any adjustment to spare in the focus mechanisms of any of then. I very much doubt that there is enough spare helix to allow them to focus to infinity with a flanged adapter. As Dave suggested in the other thread, I have considered mounting a genuine Pentax adapter semi permanently on an M42 lens, removing the locking spring clip, and drilling a hole for the locking pin in the back of the lens. Provided the rear flange of the lens is big enough this should work but I have not go around to trying it yet. Also it will be necessary to find a way to lock the adapter onto the lens mounting thread, possibly drill and tap a hole in the back of the lens. If I can get another adapter then I will try it on a cheep and sacrificial lens.

08-01-2009, 02:59 AM   #5
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Hi,

I have fixed some Takumars (and got some feedback from some readers about 35 and 50mm) using the technique described here ...

It is not really complicated, but it may take some time if you don't have a film camera for helping ...

Hope this helps

Best regards
08-01-2009, 05:39 AM   #6
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QuoteOriginally posted by Indianadinos Quote
Hi,

I have fixed some Takumars (and got some feedback from some readers about 35 and 50mm) using the technique described here ...
I followed your interesting & well presented thread, thank you for it.

Why is it necessary to remove the filter ring when adjusting infinity focus?

Dave
08-01-2009, 09:58 AM   #7
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QuoteOriginally posted by newarts Quote
Why is it necessary to remove the filter ring when adjusting infinity focus?
To get to the screws that attach the focus ring to the lens. On the left, the filter ring is attached, and the only screws you can get to are the three holding it on (red arrows) and three others attaching the lens/aperture tube to the lens. On the right, the filter ring is removed and you can see the three screws you need for adjustment, also marked with red arrows. (This lens is the Pentax-M 50mm f1.7.)

08-02-2009, 02:48 PM   #8
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QuoteOriginally posted by MattGunn Quote
... As Dave suggested in the other thread, I have considered mounting a genuine Pentax adapter semi permanently on an M42 lens, removing the locking spring clip, and drilling a hole for the locking pin in the back of the lens.
Coupl'a notes:

Some of the M42 mount lenses aren't wide enough to accommodate the latch pin hole. It's easy enough to check with a lens and camera in hand. Spot drilling works well for those lenses that have a wide enough base. Consider an intentional slight off-set for the hole so the aperture ring is easier to see beneath the flash housing.

The flange on the flanged adapters is about 0.8mm thick. I have removed the flange and shortened the adapter by that much on a lathe so that it works the same as the OEM adapter without the spring clip. When used on those M42 lenses wide enough to drill the latch pin hole you have effectively built an M-mount lens. If you remove the anodizing from the base so as to short out the AE pins you can even provide certain pseudo -A mount lens functions as described elsewhere.

H2

08-12-2009, 12:31 PM   #9
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Whilst on holiday recently I was very lucy and came across a super takumar 300mm f/4 at a BARGAIN PRICE (in need of a little work due to a bit of fungus but easily cleaned). This appears to have quite a lot of focus adjustment to spare so the flanged mount should work fine. On this lens it will really make a difference as it is rather tedious screwing the lens onto the camera as the tripod mount gets in the way. I have to be patient whilst I wait for the mount adapter though...
08-20-2009, 11:50 AM   #10
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Adapter arrived and there is just the right amount of focus adjustment on this lens to reach infinity with a flanged adapter (flange is 0.8mm thick). Now its so much and easier to mount I think I'l use it more. I'll have to see how many of my M42 lenses I can adapt and adjust this way.
08-20-2009, 01:22 PM   #11
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QuoteOriginally posted by MattGunn Quote
Adapter arrived and there is just the right amount of focus adjustment on this lens to reach infinity with a flanged adapter (flange is 0.8mm thick). Now its so much and easier to mount I think I'l use it more. I'll have to see how many of my M42 lenses I can adapt and adjust this way.
Nice that it worked on the telephoto. Still, seems moderately dangerous and far more time consuming than just screwing and un-screwing various M42 mount lenses to the camera via a proper adapter.

My 2

Regards,
Mike
08-20-2009, 01:49 PM   #12
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QuoteOriginally posted by X Man Quote
Still, seems moderately dangerous and far more time consuming than just screwing and un-screwing various M42 mount lenses to the camera via a proper adapter.
Didn't need much eventually. I screwed the mount firmly onto the lens, using an extension tube so as not to put too much force on the camera mount, and adjusted the infnity focus position on the lens. On the ST 300mm you don't even have to open the lens to adjust the focus as the locking screws are on the outside of the focus ring and reversing the process would be just as easy. In total it took about 10 min from opening the parcel containing the mount to being ready to take a photos. I think I will recover more than this much time finding, fitting and removing the pentax adapter.
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