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10-28-2013, 08:38 AM   #1
Peter Murphy

Using Pentax M Lenses on Canon DSLRs

I have acquired a collection of various Pentax M Lenses dated around the mid 1970*s. The Lenses are in beautiful condition. Can someone please advise me if "it would be worth my while in investing in a Conversion Ring to enable me to use the Lenses on the following camera. The camera is a Canon EOS 1Ds 111 FULL-FRAME DSLR. Thank you for your advise.

10-28-2013, 09:02 AM   #2
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The K to eos adapters are economical and wold be very worthwhile. There are a plethora of adapters available on ebay, at BH, Adorama, Amazon etc.
10-28-2013, 09:08 AM   #3
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Canon cameras can use Pentax lenses, you just need an adapter. Get a glassless adapter and you're good to go. Canon users often use Pentax lenses, so there are probably quite a few threads (maybe on Canon forums) and blogs about this.

Just one thing, some Pentax glass might be hard to adapt on Canon cameras due to aperture lever. Do not cut that thing off! You can simply removed it by disassembly, that way you can still sell the lens to a Pentax user some time later. It is quite sad that so much good Pentax glass gets maimed by Canon shooters.

Oh, and "full frame" or not is irrelevant, these are film lenses and film is the original medium that "full frame" is named after. Only some Pentax DA lenses might vignette on full frame, all FA and older lenses will produce a full frame image circle.
10-28-2013, 09:25 AM   #4
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Glad to hear that you are considering using those great 'legacy' lenses. You might have already read the extensive user reviews on this forum. If not, take a look:

Pentax Lenses - Pentax Lens Reviews & Lens Database

You can also read a lot of comments on the various lenses (leagacy and modern), and look at the images they capture, in the Lens Clubs section of Pentax Forums.

- Craig

10-28-2013, 09:34 AM   #5
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Be aware that there is a compatibility issue for K-mount lenses on FF Canon SLRs. The aperture actuator on the lens interferes with mirror travel. Non-FF Canon cameras do not have this problem. There are two solutions:
  • Surgery on the lens to remove the actuator lever (highly frowned on by people on this forum )
  • A minor grinding on the body's mirror that will insure clearance
Things are better with M42 screwmount lenses, but some still have deep enough rear elements to cause a problem. FWIW, this issue is long-standing for adapted lenses on Canon cameras going back 40 years or more.

10-28-2013, 10:27 AM   #6
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Though this site is oriented towards M42 glass on EOS, there is a small Pentax PK mount section.

10-28-2013, 11:58 AM   #7

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You can't use the M lenses on the 1Ds.

#1 The lever guard will have to be unscrewed off (easy) - lens won't mount with the adapter as it is obstructing the inside of the EOS mount
#2 The aperture lever will have to be removed if possible and many cases it is not and you will have to cut it. - mirror will hit the lever

I'd suggest using M42, Nikon, lenses.
Even some of the wider M42 lenses may not clear the mirror at infinity focus

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