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08-01-2009, 07:14 PM   #1
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PK mount Makinon won't focus to infinity

I'm a new K10d user, I have an old 50mm Auto Makinon PK mount lens. I'd like to use the lens (f1.7) but at the infinity mark it is only focusing about 3 feet away. The rear element of the lens moves relative to the sensor plane when focusing, I guess that's normal? I thought all the old PK lenses would work with the K10d. Appreciate any help you can give, thanks!

08-02-2009, 04:39 AM   #2
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Most likely the focus ring has slipped on the helical or the lens was disassembled and reassembled incorrectly.
08-02-2009, 11:13 AM   #3
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Thanks for reply. Focus turns from lock to lock... lens is super clean, aperture blades pristine, no scratch marks on screws above aperture ring... I wonder if there is hope for it?
08-02-2009, 01:53 PM   #4
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There almost certainly is an adjustment for infinity focus, but you may have to figure it out for yourself.

The way the rear element moves is normal. I guess there's some new technology where the rear element doesn't move, probably an effort to improve how lenses work with digital sensors. I think I've only seen one lens with a fixed rear element, the Pentax-A 35-70mm f3.5-4.5 zoom. The F version is the same optically, so make that two lenses.

08-03-2009, 02:21 AM   #5
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QuoteOriginally posted by ChildOfVision Quote
I'm a new K10d user, I have an old 50mm Auto Makinon PK mount lens. I'd like to use the lens (f1.7) but at the infinity mark it is only focusing about 3 feet away. The rear element of the lens moves relative to the sensor plane when focusing, I guess that's normal? I thought all the old PK lenses would work with the K10d. Appreciate any help you can give, thanks!
I had the exact same issue with a lovely SMC 28/2.8 lens I just bought. After a bit of googling I found various instructions (none of them specific to my problem), but I repaired it by:

1. Unscrew the decorative ring (the one that says "Ashai Pentax SMC 28:2.8")
2. You will see three tiny screws, these hold on the the filter ring. Remove these and remove the filter ring (this just pulls off).
3. Now you'll see 3 screws spaced equally on top of the focus ring. Move the focus to infinity. Carefully loosen (DO NOT REMOVE) the 3 screws. Turn the focus ring AWAY from the infinty mark (making sure the lens assy doesn't move) by a few degrees and then tighten ONE screw.
4. Now move the focus back to infinity, the len assy should have moved a fraction further in towards the sensor.
5. Attach lens to camera and try to focus to infinity.
6. Rinse / repeat steps 3 - 5 until you can get sharp focus at infinity.
7. Once you're happy with the focus, tighten all 3 screws, re-attach the filter ring, screw in the decorative ring.

I set mine to focus just past infinity and it's hardly impacted the shorter focal distances.

It's easier to do then explain. Basically as you move the focus ring you'll see which way the lens assy moves, you just need to make the lens assy move a smidgen more towards the camera sensor.

Carl
08-03-2009, 04:11 PM   #6
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Thanks so much for all the help everybody. Carl, I'll try the instructions this week and post my results. Again, thanks for all the speedy replies!
08-16-2009, 04:58 PM   #7
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Thanks for the help everybody, but for whatever reason I still couldn't get the Makinon to focus properly. Following Creid's instructions I adjusted the infintiy point, but as the elements moved back, towards infinity focus, they bound up with the aperture pin and I couldn't adjust it back any further. Only focused about 5 feet away and that was as good as I could get it, which taking into account the quality of the lens, wasn't really worth much more time. Oh well.
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