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07-22-2016, 07:06 PM   #1
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8-element Super Takumar 50mm/1.4 on the K-S1 question

I recently bought the 8-element Super Takumar 50mm/1.4 and use it on my Samsung NX20 camera. If I adapt it to my K-S1, will the mirror hit the protruding rear element when focused to infinity? I've read it happens on some DSLRs. Thanks!

07-22-2016, 07:11 PM   #2
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I do not know for sure, but, I am 92.93% sure that the mirror will not hit the rear element. The M42 lens is designed to fit natively on pentax M42 FF cameras and with a simple adapter fit on K mount (with no change in registration distance). The problem emerges in cameras with a shorter registration distance such as canon. This is why canon users 'hack' the rear assembly of K mount lenses and use specific adapters to avoid damaging the rear element.

But I am 'unsure' only because I have not tried the combo you speak of. I rely on the idea that M42 lenses are meant to work as designed on K mount cameras with the right adapter.
07-22-2016, 07:28 PM   #3
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QuoteOriginally posted by Wild Mark Quote
I do not know for sure, but, I am 92.93% sure that the mirror will not hit the rear element. The M42 lens is designed to fit natively on pentax M42 FF cameras and with a simple adapter fit on K mount (with no change in registration distance). The problem emerges in cameras with a shorter registration distance such as canon. This is why canon users 'hack' the rear assembly of K mount lenses and use specific adapters to avoid damaging the rear element.

But I am 'unsure' only because I have not tried the combo you speak of. I rely on the idea that M42 lenses are meant to work as designed on K mount cameras with the right adapter.
Thanks Mark!
07-22-2016, 07:32 PM - 1 Like   #4
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QuoteOriginally posted by alex-virt Quote
I recently bought the 8-element Super Takumar 50mm/1.4 and use it on my Samsung NX20 camera. If I adapt it to my K-S1, will the mirror hit the protruding rear element when focused to infinity? I've read it happens on some DSLRs. Thanks!
Mine hasn't been a problem on my K-3 or K-mount film cameras, but I don't have a K-S2

QuoteOriginally posted by Wild Mark Quote
I do not know for sure, but, I am 92.93% sure that the mirror will not hit the rear element. The M42 lens is designed to fit natively on pentax M42 FF cameras and with a simple adapter fit on K mount (with no change in registration distance). The problem emerges in cameras with a shorter registration distance such as canon. This is why canon users 'hack' the rear assembly of K mount lenses and use specific adapters to avoid damaging the rear element.

But I am 'unsure' only because I have not tried the combo you speak of. I rely on the idea that M42 lenses are meant to work as designed on K mount cameras with the right adapter.
If I understand the rule correctly, anything after a late SV (1962 -1968) is OK with the 8-element. An SV with orange R on the rewind crank assembly is 'late'; a green R is early, and the mirror hits the rear element.*

PF SV Camera Review - See the Comment text in the Data table

I haven't tested the rule on my late SV.


Last edited by monochrome; 07-23-2016 at 03:24 PM.
07-22-2016, 07:55 PM   #5
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Thanks Monochrome! If it works on the K-3 I guess it will be OK on the K-S1 too.
07-22-2016, 08:46 PM   #6
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Yes, I forgot that Monochrome. thanks for the reminder.
07-23-2016, 08:50 AM   #7
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QuoteOriginally posted by Wild Mark Quote
I do not know for sure, but, I am 92.93% sure that the mirror will not hit the rear element. The M42 lens is designed to fit natively on pentax M42 FF cameras and with a simple adapter fit on K mount (with no change in registration distance). The problem emerges in cameras with a shorter registration distance such as canon. This is why canon users 'hack' the rear assembly of K mount lenses and use specific adapters to avoid damaging the rear element.

But I am 'unsure' only because I have not tried the combo you speak of. I rely on the idea that M42 lenses are meant to work as designed on K mount cameras with the right adapter.
This was my original thought, also .... but then I thought, "Why trust years of Pentax engineering when I can actually look for myself?", so I took the lens off my K-30 {currently my only working K-mount camera}, turned it on, and put it into LV mode {which has the effect of lifting the mirror}. When fully lifted, the mirror comes out to the ridge I marked with an orange arrow; it occurs to me that those clever Pentax engineers designed the camera so that ridge would prevent a lens from protruding into where the mirror could hit it, but then I took some measurements; the ridge is approximately 5mm from the mount edge, and my Super Tak 50mm lens protrudes 4mm behind the mount when focused at infinity, so I guess this is safe enough.

{and I'm guessing that all recent consumer-level Pentax cameras - including the K-S1 - use the same mirror-box design; engineers tend to be conservative, which means, amongst other things, not redesigning something which meets current needs}


07-23-2016, 09:12 AM   #8
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Thanks reh321! I repeated your measurement on my K-S1 and got about 7mm, so it should work OK. I'm planning to use a flange adapter, and it probably won't achieve infinity anyway.

07-23-2016, 06:12 PM   #9
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QuoteOriginally posted by alex-virt Quote
Thanks reh321! I repeated your measurement on my K-S1 and got about 7mm, so it should work OK. I'm planning to use a flange adapter, and it probably won't achieve infinity anyway.
Yeah, reading those numbers is kind of tricky.

If you use either the official Pentax one, such as the ones mikeSF is selling on the PF Marketplace
https://www.pentaxforums.com/forums/24-photographic-equipment-sale/326400-sal...ml#post3719457
or even a modern Chinese copy, it should work as it did when new. When we visited Henry Ford's "Greenfield Village" in May, I disciplined myself to use only an M42-mount lens all day {I have a Chinese adapter ring}, and except with having to work at focusing, using that lens was just like using a comparable K-mount lens.
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