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11-06-2012, 06:46 PM   #1
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Canon FD to PK Adapters... any good?

Just how bad is the image degradation when using one of the optical adapters? The recent 'share your prettiest lens' thread made me re-examine a pristine old Sigma 135mm f/3.5 I picked up for nothing last year, and now I'm half nosy to see just what results I may get from the thing.

I know shoving an extra bit of glass in the mix will negatively effect the quality of the results, but I'm curious as to just how badly. If its not too severe, I'd be willing to drop the $30 or so on an adapter if it means allowing the lens to get some use.

If it IS decent, it would be a lens I'd keep an eye out for in a Pentax mount (I know that they exist, even if I'm not seeing any around at the moment). The lens is so compact (its a bit over half the size of my other 135's) that I could see it being a fun match for the K-30 when I get around to buying it.

11-06-2012, 07:18 PM   #2
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Keep in mind the adapter works like a short tele-converter.

FD 50/1.8 @ 1.8




FD 50/1.8 @ 8




FD 50/1.4 @ 1.4




FD 50/1.4 stopped down




FD 50/1.4 @ 1.4




FD 50/1.4 stopped down


11-06-2012, 07:59 PM   #3
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Hrm. Not bad at all stopped down - definitely acceptable at least. Are there any particular adapters to look for? I noticed two or three different styles when I went pricing them.
11-06-2012, 08:05 PM   #4
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This is the one I have...it's a Scoptic from Success Optics.







That screw that sticks out is what presses on the aperture lever so that the lens stops down. It's moved by a ring on the adapter that acts like the A/M switch on a screw mount lens.

The glass element is removable for macro use.

11-07-2012, 05:17 AM   #5
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Just remember that because the converter has lenses for infinity focus correction, for the canon adapter it adds 1.45x magnification and loss of one whole stop.
11-07-2012, 09:08 AM   #6
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So a 135 would become roughly a 310mm after the APS-C crop factor is added in as well if I'm doing the math right in my head?
11-07-2012, 11:20 AM   #7
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QuoteOriginally posted by Sagitta Quote
So a 135 would become roughly a 310mm after the APS-C crop factor is added in as well if I'm doing the math right in my head?
And my Vivitar 28mm becomes a 60mm. It's not as bad on my K1000 (40mm).
11-07-2012, 01:26 PM   #8
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Is it one of these - of course this is MD mount:


I was curious about that one but sold it quick before it took hold. I made $12.47 profit!

11-07-2012, 02:09 PM   #9
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There is more info in the adapter-thread.
You can also remove the glass very easily. Then you get no optical losses, no light losses, but no infinity, but it may be of interest if you want to use the Canon FD 50, 100 and 200mm macro lenses. For the 200mm macro you can focus up to something like 3m, which is fine for butterflies or similar.
11-07-2012, 03:02 PM   #10
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QuoteOriginally posted by Sagitta Quote
So a 135 would become roughly a 310mm after the APS-C crop factor is added in as well if I'm doing the math right in my head?
Forget the crop factor, deal with true focal lengths, your 135 would be a 200mm
11-07-2012, 07:21 PM   #11
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QuoteOriginally posted by Just1MoreDave Quote
Is it one of these - of course this is MD mount:


I was curious about that one but sold it quick before it took hold. I made $12.47 profit!
That's the same lens. The Canon I have has the big silver base like a lot of those old FDs have. Mine is one of those cases where you open the package (in this case, the lens case) up and then have to wonder if the lens ever was actually used. As I said, the size is what intrigues me. If the thing has decent quality results, I'd snap one up in a heartbeat if I ever spotted it in K-mount.
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