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07-20-2017, 03:38 AM   #1
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New Canon shooter wanting to use Pentax lenses

I am a long time Pentax user - K10D, K-3, Pentax Spotmatics with an assortment of K-mount and screw mount lenses.
I have recently acquired two old but still capable Canon DSLRs - EOS-1DS (full frame) [EF] and EOS-20D [EFS]. Each one only has a kit lens.

If I wanted to use some of my Pentax lenses, what is the recommended approach? Should I buy a K-mount to EOS adapter which would let me use my K-mount lenses. I have a genuine Pentax K-mount to M42 adapter so could I then use that to mount a screwmount to the K to EOS adapter? Or would that prevent infinity focus? Or should I just buy two adapters? They are not all that expensive.

Any advice would be appreciated. I am out of my depth here.

07-20-2017, 04:11 AM   #2
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Some adapters may appear to be cheap, but they can be nasty too!...Those thin ring adapters can be very difficult to take off a K mount.
07-20-2017, 05:18 AM   #3
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I'd say get the best quality ones you can get, and with the M42 ones find genuine Pentax ones, then use them in manual focus.
07-20-2017, 05:24 AM   #4
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I have no experience with this myself, but everything I've read indicates that if you want to use your K-mount lenses on the 1Ds, you'll need to remove or shave down their aperture levers (to avoid hitting the mirror box), making them thenceforth useless on K-mount cameras. The 20D, being an EF-S camera, should not have the same problem.

07-20-2017, 06:16 AM   #5
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I would get a K-EOS adapter that has a dandelion chip, like this one (not an affiliate link).

As for the M42 lenses, I would recommend a second M42-EOS adapter. Because of the larger mount and shorter registration distance, M42-specific adapters are a lot more solid and can use the strength of the full mount on EOS, unlike K-mount, where you have the M42 adapter stuck in the mount, or you have it just held by the mount's springs.

Last edited by timw4mail; 07-20-2017 at 06:19 AM. Reason: M42 suggestions
07-20-2017, 04:18 PM   #6
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QuoteOriginally posted by surfar Quote
Some adapters may appear to be cheap, but they can be nasty too!...Those thin ring adapters can be very difficult to take off a K mount.
Thanks. Cheap and nasty is what I try to avoid (from experience). I will take your advice.

QuoteOriginally posted by VoiceOfReason Quote
I'd say get the best quality ones you can get, and with the M42 ones find genuine Pentax ones, then use them in manual focus.
Thanks. I will go for good quality. Yes, I have the genuine Pentax M42 -> K-mount adapter. Non-genuine looks the same but it isn't!!

QuoteOriginally posted by Scintilla Quote
I have no experience with this myself, but everything I've read indicates that if you want to use your K-mount lenses on the 1Ds, you'll need to remove or shave down their aperture levers (to avoid hitting the mirror box), making them thenceforth useless on K-mount cameras. The 20D, being an EF-S camera, should not have the same problem.
I was not aware of that problem with the 1Ds. Thanks for that. I'll do more investigation on that one.

QuoteOriginally posted by timw4mail Quote
I would get a K-EOS adapter that has a dandelion chip, like this one (not an affiliate link).

As for the M42 lenses, I would recommend a second M42-EOS adapter. Because of the larger mount and shorter registration distance, M42-specific adapters are a lot more solid and can use the strength of the full mount on EOS, unlike K-mount, where you have the M42 adapter stuck in the mount, or you have it just held by the mount's springs.
Thanks for your help. Very useful advice. If I decide to go down this road I will get two adapters but I will get a K-EOS adapter first and see how that goes. If it goes well then I will consider an M42 later.
That's a very nice collection of lenses you have there, Tim.

Thanks again all for your help and assistance.
07-21-2017, 04:07 PM   #7
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I have since been talking to another Canon shooter and have also done more reading on this subject. As the Canon cameras will not be able to use the aperture lever on the K-mount lenses they can only be used wide open unless they have an aperture ring and only one of mine does. So that rules out using K-mount as far as I am concerned.

So, now I am just looking at getting an M42 to EOS adapter because I know that they will work as they all have aperture rings and they will work in stop down mode. And the good ones have focus confitmation.
I think I am on the right path now. I have a good collection of Takumar primes so I am looking forward to having some fun.

07-21-2017, 04:40 PM   #8
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QuoteOriginally posted by rayallen Quote
I have since been talking to another Canon shooter and have also done more reading on this subject. As the Canon cameras will not be able to use the aperture lever on the K-mount lenses they can only be used wide open unless they have an aperture ring and only one of mine does. So that rules out using K-mount as far as I am concerned.

So, now I am just looking at getting an M42 to EOS adapter because I know that they will work as they all have aperture rings and they will work in stop down mode. And the good ones have focus confitmation.
I think I am on the right path now. I have a good collection of Takumar primes so I am looking forward to having some fun.
The way most of those adapters work, I think you'd actually have the aperture completely closed if you lack an aperture ring.
07-21-2017, 08:11 PM   #9
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QuoteOriginally posted by rayallen Quote
an M42 to EOS adapter
The ones on OZZY ebay are fine....around 2-3 bucks gets you a ring AND a cap....I use my Takumars with them and a speedbooster with EF to Fuji.
07-21-2017, 08:40 PM - 1 Like   #10
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QuoteOriginally posted by timw4mail Quote
The way most of those adapters work, I think you'd actually have the aperture completely closed if you lack an aperture ring.
Of course, you are right. What was I thinking?? The standard position on a K-mount lens is minimum aperture.

QuoteOriginally posted by surfar Quote
The ones on OZZY ebay are fine....around 2-3 bucks gets you a ring AND a cap....I use my Takumars with them and a speedbooster with EF to Fuji.
Thanks for that. I am about to order one right now.
07-22-2017, 02:58 AM   #11
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I use M42 lenses occasionally on a couple of Canon film SLRs using a cheap ebay adapter. It works but I had to drill the locking hole in the adapter to make it big enough for the locking pin on the camera to fit in it. I've also had some battery problems with it and suspect that the adapter causes the battery to drain even when the camera is off. Still, I like using old manual lenses and such things don't exist in EOS mount.

I would use k-mount lenses on a Canon SLR though as I understand that the aperture stop-down lever needs to be removed, something most people do by cutting it off (horror!!) though it can be done reversibly if you're willing to open the lens up.
07-22-2017, 03:59 PM   #12
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QuoteOriginally posted by Jonathan Mac Quote
I use M42 lenses occasionally on a couple of Canon film SLRs using a cheap ebay adapter. It works but I had to drill the locking hole in the adapter to make it big enough for the locking pin on the camera to fit in it. I've also had some battery problems with it and suspect that the adapter causes the battery to drain even when the camera is off. Still, I like using old manual lenses and such things don't exist in EOS mount.

I would use k-mount lenses on a Canon SLR though as I understand that the aperture stop-down lever needs to be removed, something most people do by cutting it off (horror!!) though it can be done reversibly if you're willing to open the lens up.
Thank you, Johnathan. I will let you know how my M42 adapter works when it arrives.

Re K-mount lenses, I am not about to modify any of mine as they work just fine on my Pentax bodies and that is where I will contiue to use them. I expect that I will be able to use my Takumars on the Canons without modifications and that will give me more lens options there. That should keep me happy.
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