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10-30-2011, 04:29 PM   #1
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canon fd - pk adapter question?

I was wondering if anyone that has or has had a canon fd lens to pentax pk body adapter could anwser a question. So far as I can tell, they only make the kind with corrective glass. As best as I can tell looking at pictures on ebay, there is a fairly thick ring in the middle to allow for the glass. Is that correct? I am considering making my own adapter with no glass that is minimum thickness to minimise loss of distant focus. Best I can find for parts (so far) isn't going to be much cheaper than a fd-pk adapter so I would rather just buy one and remove the glass, unless I am going to be able to achieve further focus on a home made one.

Does anyone have and opinion on doing this?

10-30-2011, 04:41 PM   #2
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The canon FD system has a shorter registry distance buy about 5mm so jif you can even just make a minimum mechanical attachment you will give up about 10mm on focus distance. For most lenses except extreme telephoto, this means they will work as macro only

Wthe glass converts thie adaptor to a 1.4x teleconverter
10-30-2011, 05:59 PM   #3
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The lens in question is a vivitar 90mm 2.5 bokina. From what I have read (assuming it is right), with the glass removed from an adapter, it will focus out to about 9 feet. I was hoping for more like 15-20 feet but I'll take whatever I can get. Fyi I know that it is prized as a macro lens but it is suposed to be very good at any range too and I just wanted to try it out. I don't want to go hacking the mount as I will probably eventually sell it to someone that can appreciate it more for its macro capabilities and or has a camera that can get infinity focus with it. that is unless I can not get enough money for it when I try and sell it, in which case, it might just get modded (I would have to think long and hard about that due to its value though). I did call around to some shops about selling it (consignment etc) and didn't really like what I heard but they didn't actually see the lens so perhaps they were just being cautious and conservative.

I would also like to have such an adapter just to have (maybe to get some use out of some of those lenses that are waiting to be modded).

One other option would be to buy and mod the matching 1:1 adapter (they seem to be more comon and a lot cheaper) but I don't know exactly how the 1:1 adapter works (do you loose infinity focus with it, and does it change the focal length much)?
10-30-2011, 05:59 PM   #4
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Without the glass the focusing distance with a 50mm lens is just a few inches. I think a let of the thickness is to accommodate the breech-lock mount.

Canon FD Adapter - a set on Flickr

Canon FD 50 1.4 - a set on Flickr

Vivitar 28mm

April 22, 2010 - a set on Flickr

10-30-2011, 06:10 PM   #5
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QuoteOriginally posted by boriscleto Quote
Without the glass the focusing distance with a 50mm lens is just a few inches. I think a let of the thickness is to accommodate the breech-lock mount.

Canon FD Adapter - a set on Flickr

Canon FD 50 1.4 - a set on Flickr

Vivitar 28mm

April 22, 2010 - a set on Flickr
That kind of makes me wonder if the information I found about this lens focusing to about 9 feet might be wrong.
10-30-2011, 06:17 PM   #6
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It would seem you are right. I just tried and with the lens hand held as far into the camera as it can go, I'm only getting about 3-4 feet so any thickness the adapter would add would make it even less than that. At least I found out before i spent any money trying it. Its also too bad that there are not adapters with good glass (it would have to be very good to justify using it with this lens).
10-30-2011, 06:21 PM   #7
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If you're thinking of making your own mount, you must be handy...

So why not just hack off the FD mount behind the aperture ring and screw a K-mount flanged adapter onto it. It's been done before! You'd need to use a spring to hold the aperture-lock levers so it would actually stop-down to the desired aperture when you turn the ring, and then your only worry would be adding enough distance to get back to the Pentax registry distance.
10-30-2011, 06:47 PM   #8
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QuoteOriginally posted by panoguy Quote
If you're thinking of making your own mount, you must be handy...

So why not just hack off the FD mount behind the aperture ring and screw a K-mount flanged adapter onto it. It's been done before! You'd need to use a spring to hold the aperture-lock levers so it would actually stop-down to the desired aperture when you turn the ring, and then your only worry would be adding enough distance to get back to the Pentax registry distance.
I was thinking more along the lines of mating two adapters together with perhaps a very thin flange in the middle, or even something like flatting the back of some sort or fd adapter and then braze or solder an infinity focusing m42-pk adapter to the back. Tearing the mount off an fd mount camera for parts also crossed my mind but it seems they are less common (cheap anyway).

I have already converted canon, minolta, olympus and nikon mount lenses with infinity focus but I prefer to remove the mount entirely, screwing on a new mount (off a donor lens or a pk-macro adapter). The thing is, this lens could be worth couple of hundred dollars as is so I'm a lot more reluctant to go hacking it. The cheapest I have seen one go for searching was 140$ on ebay for fd mount like mine without the adapter, from a seller that claimed to know nothing about cameras and didn't know if it worked. The cheapest completed listing right now is170$ with the macro adapter but the lens has haze and scratches and the macro adapter had fungus. The next cheapest was 230$ for m42 mount with the macro adapter (defanatly worth more than mine) so its value falls somewhere in the middle I would think. Mine is in very nice condition.

10-31-2011, 01:41 AM   #9
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It's a tough decision. Try to mod (and maybe ruin) a lens with some value, or sell it and find something comparable for a bit more money? I ended up selling all my FDs (for a very good profit) rather than try to mod them. My gut feeling is, if the lens is worth enough to worry about, sell it and find a PK version.
10-31-2011, 02:10 AM   #10
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There are more info on this adapter in the adapter-thread. To answer your specific question: it is easy to remove the optics from that adapter, and considering the low price, it is not a big thing that they don't sell the non-optical version in K mount (they do in Nikon mount for instance). As others pointed out, the optic-liberated adapter and the difference in registration distance work as a thin extension tube, so you loose infinity focus. On the Canon FD 200mm macro lens you can focus to almost 3m, which is enough for most macro work. For a 90-100mm macro it will be less. Weather it is worth it is up to you. The adapter is well made, and the close down ring works well, even though the optics are nothing to brag about (but what can you do in that short space, with what I think is only two cemented lens elements). In case you go the bath of modifying the lens permanently, there are examples of FD conversions and good advices in the impossible lens club.
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