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04-27-2009, 11:46 PM   #1
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Lens Surgery

I have a few older Canon FD and Contax (Yashica) mount lenses in my lens collection and apart from gathering dust they aren't doing much...and I have a few spare K mounts...I have been eyeing my 85mm f/1.2 with renewed interest.

Is it difficult to convert canon FD mount lenses to K mount?

04-28-2009, 05:34 AM   #2
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I don't have an answer, but I do have a question.
What do you mean when you say that you have a few spare K mounts? Are they old lenses that you are scrapping to attach in some way the canon lens , or what?
Just intrigued..
04-28-2009, 06:16 AM   #3
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Look up lens register distances before you go too far - if the distance is greater than the M42 standard you might not be able to get infinity focus
04-28-2009, 07:01 AM   #4
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QuoteOriginally posted by Nesster Quote
Look up lens register distances before you go too far - if the distance is greater than the M42 standard you might not be able to get infinity focus
that's actually a good point, but fortunately I know how to adjust the focus slightly forward/backwards on FD lenses..but the draw back of that is that I will have to completely disassemble the lens to do it.

In regard to having spare K mounts I have been given a few Rikenon,Vivitar and Tamron lenses that are in various states or disrepair and I intend on transferring the bayonet mounts.


PS, I recently discovered the canon FD mount flange is about 42mm, putting it just a tad short of Pentax's 45.46mm...it might be a stretch but I'll see what I can do about this..

I also have a Canon 14mm f/2.8L rectilinear ultrawide lens which if this experiment proves successful, will be my next victim.

the flange for Contax lenses is 45.50mm so converting these lenses should be a breeze..


Last edited by Digitalis; 04-28-2009 at 07:33 AM.
04-28-2009, 08:43 AM   #5
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Hi Digitalis-man,

about the CY conversion
please have a look here,
Which CZ MM lens would you buy for <$400? - FM Forums
Other than that there are ready-made lensbacks from
Zeiss Contax lens for Pentax cameras

About the Canon FD lenses, some random links I could find (afaik they deal with FD to EOS conversion)
Canon FD 85mm f/1.2 L vs SSC - FM Forums
Canon FD 85L Converted to F-mount ( Nikon )--Do-able? - FM Forums
Canon FD 1,2/85mm SSC aspherical - FM Forums
5D + Canon FD 1,2/85mm ssc aspherical on Flickr - Photo Sharing!

But hey, this should make you realize that LBA's a devil,
It's been fun - FM Forums

Beware! Georg (devil's advocate)
04-28-2009, 08:56 AM   #6
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oh bugger, the FD 85mm f/1.2 has a floating lens element...that sounds like it could be more trouble than it's worth.

and this isn't LBA, my mother bought this lens years ago when she was working as a photojournalist, I just want to revive this lens.

apparently people using this lens on the 5D have to shave their mirrors otherwise the mirror kisses the lens's arse on the way up...fortunately the K10D is APS-C and it should not have to suffer this indignity.
04-28-2009, 09:53 AM   #7
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QuoteOriginally posted by Digitalis Quote

and this isn't LBA, my mother bought this lens years ago when she was working as a photojournalist, I just want to revive this lens.
Why not just use an F1n or AE-1 and shoot film?
04-28-2009, 11:46 AM   #8
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'bout a year ago I performed sex-surgery on a Tamron-F 300/5.6 in Olympus configuration and adapted it to Pentax-K with a P/K bayonet mount salvaged from a defunct lens.

I didn't have a lathe available at the time to shave the new mount to the appropriate thickness (thinness?) to focus to infinity so I made lemonade and accepted a focus range of roughly 3-167 feet. That was fine as I wanted to experiment with pseudo-macro images and extention rings anyway.

Another expedient in that case was to simply epoxy the mount to the lens base after removing the Oly bayonet fitting.

Results were satisfactory and consistent with the original capability of the lens.

[Random thought - I have NEVER intentionally focused on anything at infinity. I can't see that far!]

Appended: 1st pix at 22 ft, ISO 800, f8, 1/1000, SR @ 450.

H2

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04-28-2009, 01:17 PM   #9
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QuoteOriginally posted by Digitalis Quote
Is it difficult to convert canon FD mount lenses to K mount?
I just converted a Vivitar 55mm f2.8 macro from FD to K. It wasn't too hard but it all depends on what compromises you can live with in the finished product.

Despite removing some of the FD mount, tacking on a K mount added more thickness than I needed. I ended up with a lens that can only focus to five feet maximum. For a macro, this hardly matters and is sort of a permanent short extension tube, but for an 85mm, it would be severely limiting.

The mount that I removed had the only mechanical linkage between the aperture ring and the aperture. Without it, the lens was permanently wide open. I had to improvise a connection. The aperture ring now adjusts the aperture but the marked stops are all wrong. I can stop down more than the original lens, though. That's useful for macro.

I was hoping that with a third-party lens, the conversion would be simpler. Why shouldn't Vivitar/Komine make it easy on themselves to adapt their production? Apparently they never thought of it or they had a reason not to. My investment is only $10 so I had little risk. I would have been less willing to hack up a really good lens even if I couldn't use it.
04-29-2009, 05:27 AM   #10
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Found one more with drawings and all:
FD 85L f/1.2: a real gem

This is for the L-version, not the S.S.C.

Digitalis, if you could keep us updated on your efforts I would appreciate it.

For a start I'd like to know if you have the L or the S.S.C. ?
And, if you could measure the diameter of the rear lens with housing in order to tell if it is physically possible to pass through a PK-mount ?

Thanks, Georg (the other)
04-29-2009, 08:19 AM   #11
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QuoteOriginally posted by georgweb Quote
Found one more with drawings and all:
FD 85L f/1.2: a real gem

This is for the L-version, not the S.S.C.

Digitalis, if you could keep us updated on your efforts I would appreciate it.

For a start I'd like to know if you have the L or the S.S.C. ?
And, if you could measure the diameter of the rear lens with housing in order to tell if it is physically possible to pass through a PK-mount ?

Thanks, Georg (the other)
The lens version I'm working with is the 85mm f/1.2L - the focusing should be fine...I can get it to focus on where infinity should be on a K mount lens...however the Aperture on the FD lens is giving me trouble because it works the other way around from the Pentax K mount lenses typically do.

So I'm going to be doing some experiments, the Pentax K mount does fit but a lot of the outer diameter of the lens isn't covered by the mount which could cause problems with dust and contaminants getting into it...I'll have to remedy that. Fortunately, I have access to a lathe. I'm thinking of making a groove in the lens for an o ring to seal it...the way I did it with one of my 50mm f/1.2 lenses a few years ago (I was working in dusty conditions, and dust can gum up lens mounts REAL bad)...I"ll have to find that lens, not to mention a few other modifications I have done to lenses over the years. I have actually made completely new hoods for some of my lenses because the originals just didn't do the job properly.

I have a die hard canon photgrapher friend who was more than a bit ticked off that he couldn't use his FD lenses on the current digital SLRS...so I intend on ticking him off even more by using an FD lens on my pentax DSLR
04-29-2009, 08:56 AM   #12
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there have been people who done some mods to their DSLR to accept Contax lenses, but you would have to search around.
04-29-2009, 10:21 AM   #13
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I've converted an FD lens to Pentax K bayonet - it is manual stop-down now because of incompatible aperture lever rotation directions.

The FD lens must be shortened to get the registry distance right, but removing the FD mount usually shortens the lens quite a bit. As I recall, the main difficulty I had was in light sealing the lens after the K-mount was attached.

Iowa Dave

My advice is to do the C/Y -> K swap first.
04-29-2009, 11:43 AM   #14
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I find myself with a slew of FD lenses (bought with eBay cam lots, destined to be resold Real Soon Now), the best of which are probably the FD-24/2.8, FD-50/1.4, FD50/1.4-SSC, FD-135/2.8, FD-135/3.5, and FD-200/4-SSD. But I already have fine Pentax glass in those ranges: M28/2.8, FA50/1.4, M55/1.8, B135/2.5, S200/4. And a Viv24/2. Are any of those Canons worth suffering my inept surgical skills?
04-29-2009, 07:21 PM   #15
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QuoteOriginally posted by newarts Quote
I've converted an FD lens to Pentax K bayonet - it is manual stop-down now because of incompatible aperture lever rotation directions.

The FD lens must be shortened to get the registry distance right, but removing the FD mount usually shortens the lens quite a bit. As I recall, the main difficulty I had was in light sealing the lens after the K-mount was attached.

Iowa Dave

My advice is to do the C/Y -> K swap first.


yeah I'm discovering that right now, these light leaks are a real pain..but I'm getting on top of them.

I can convert Contax quite easily...this canon FD lens is just taking longer than I expected...pics will be forthcoming...
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