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12-24-2018, 11:27 AM   #1
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Focus issues with old M42 lenses

Merry Christmas everyone!!
I have a K500 and I also have a number of M42 non Pentax lenses that I would like to use on the K500.
I know I have used a couple of these lenses before on an older Pentax DSLR and everything worked fine in manual mode.
The issue with the K500 is that these lenses will only focus close up. It is impossible to get Infinity focus.
I've looked for online information but have come up empty.
I have the M to K adapter and the Aperture Ring Function is set to Enable
Thanks for any input you may have on this.
Again Merry Christmas

12-24-2018, 11:36 AM - 1 Like   #2
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Does the adapter have a flange which partially covers the camera mount? Flanged adapters move the lens farther from the sensor plane and thus infinity focus becomes impossible. Essentially it is a very short extension tube making the lens close focusing.

This is what it sounds like you have.
12-24-2018, 11:38 AM   #3
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M to K is an incorrect adapter. The proper adapter is ďadapter KĒ

If you screw your adapter in and mount the M42 lens there should be no gap between lens mount and the adapted flange.

The loss of infinity indicates your lens is too far away from the mount (like an extension tube).
12-24-2018, 11:42 AM   #4
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Exactly which adapter are you using? A third party flanged adapter (has a flange that lock into the standard k-mount locking pin) will not have focus to infinity. The genuine Pentax adapter and third party copies does not have this external flange and lock in place with a spring on the adapter. Additionally some adapters have an internal flange to push in the aperture stop down pin on auto lenses. Later m42 lenses with a aperture info lever and tab will not screw in far enough on these adapters to allow focus to infinity.

12-24-2018, 12:15 PM   #5
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This one allows infinity focus: Pentax M42 Screw Mount to Pentax K-Mount Adapter ***** | eBay

This one does not: M42 Lens to PK K Mount Adapter Ring For Pentax Camera K-1 K-3 K-3II K-50 K-70 K7 155397368902 | eBay

If your adapter looks more like the second one that the first, that is your problem.
12-24-2018, 01:06 PM   #6
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Thanks VERY MUCH guys. I did some more head scratching and was watching a YT video where a guy is showing how to attach an M type lens to the Pentax DSLR. As soon as I saw the adapter he was using my memory clicked and it is exactly what my issue is, as you all explained. I have one of those thin adapers but can't find it right now so I will get one. The adapter I was trying to use (unsuccessfully) is a much thicker unit. It is Japanese and is labelled "For Pentax K/M"
Thanks again for helping me solve the problem.
I don't suppose you can help me remember where I hid that thin adapter away for safe keeping........
Never mind.
Merry Christmas
12-24-2018, 01:08 PM   #7
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FYI

M42-PK adapters - some personal experiences
12-24-2018, 01:36 PM   #8
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Very good insight. Thanks much
Merry Christmas

12-24-2018, 04:01 PM   #9
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QuoteOriginally posted by BerndM Quote
I don't suppose you can help me remember where I hid that thin adapter away for safe keeping........
Never mind.
Merry Christmas
Itís right next to where you put the.................I forgot what I was going to say! 😉 Merry Christmas!
12-24-2018, 04:05 PM   #10
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Been there, done that
Too many times
Best Christmas Wishes 2 U
12-26-2018, 06:05 AM - 1 Like   #11
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You left it in the first place youíll look after you get shipping confirmation on its replacement...

-Eric
12-26-2018, 06:21 AM   #12
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I was going to add

" it will be in the last place you will look "

but I like Eric's post better

so I won't
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