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01-21-2013, 05:59 PM   #1
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Is FD lens on K-01 (without glass adapter) and focus to infinite possible?

Hi, I was wondering if the glass is needed on the FD adapters with the K-01 and would it still achieve infinite focus. I have been goggling for days without luck and I have not seen any glassles adapters for FD except for the Sony nex. Has anyone modified an adapter with success?
Thanks in advance and sorry if this has been discussed, I did do forum searches but couldn't find anything helpful.

01-21-2013, 06:01 PM   #2
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QuoteOriginally posted by dmb video Quote
Hi, I was wondering if the glass is needed on the FD adapters with the K-01 and would it still achieve infinite focus. I have been goggling for days without luck and I have not seen any glassles adapters for FD except for the Sony nex. Has anyone modified an adapter with success?
Thanks in advance and sorry if this has been discussed, I did do forum searches but couldn't find anything helpful.
Nikon lenses will focus to infinity, but you'll get crappy IQ because of the 1.4x teleconverter that's built-in to the adapters that are out there.

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01-21-2013, 06:07 PM   #3
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Thanks for your reply Adam. Its the canon fd lenses I want to convert but without the optical glass correction if possible, I assume it has to be possible with the mirror-less K-01 as sony nex users are able to. I have adapters as is for fd to eos - but I don't like the results when I shoot wide open and I am convinced its the adapters messing up the image.
01-21-2013, 06:22 PM   #4
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The adaption depends a lot on the flange distance and size of mount. Simply not having a mirror does not guarantee you can adapt anything you want. Well, unless you really go to work and make a frankenstein camera.
Usually we get Canon shooters that want Pentax lenses, but you might want to search the forums if anyone has already tried what you are attempting to do.

01-21-2013, 06:24 PM   #5
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QuoteOriginally posted by Adam Quote
Nikon lenses will focus to infinity, but you'll get crappy IQ because of the 1.4x teleconverter that's built-in.
What?
01-21-2013, 06:29 PM   #6
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QuoteOriginally posted by Na Horuk Quote
Usually we get Canon shooters that want Pentax lenses,.
Ha - guilty I own three canon dslrs and a ton of pentax glass - both m42 and K-mount - which is why buying the k-01 was an easy decision at the recent price drop. I have a couple of really nice FD lenses that I think would be amazing on the Pentax - there has to be something -
On another note, I have some enlarger lenses (M39) arriving soon - I think I will need a bellows to make them work on the k-01 - that will be another thread Im sure :
thanks for your reply
01-21-2013, 06:32 PM - 1 Like   #7
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FD lenses are not adaptable to K-mount without the use of glass elements or without losing infinity focus.
The K-01 uses the old K-mount and retains the flange distance which is longer than the flange distance of the FD mount.
I believe that Pentax and Nikon use nearly the same flange distance which is one of the longest of all the major 35mm SLR mounts.
I've read that the K mount and F mount are so similar that you can mount F mount lenses directly to the K mount ( I haven't tried and I'd do more research before trying)
01-21-2013, 06:40 PM - 1 Like   #8
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FD lenses will not focus to infinity on a Pentax with a glassless adapter. A 50mm lens without the glass will focus to a few inches. Telephoto lenses might focus to a few yards. Pre-AI Nikon lenses can be force fit and will focus to infinity. AI lenses need some modification. Nikon auto focus lenses will not fit without and adapter. RioRico was our resident mad scientist when it came to adapting lenses. Sadly he has not been able to post since last spring.

The Canon FD adapter is a 1.42x tele extender, the Nikon adapter is about 1.25x. With the Canon adapter you lose 1.5 stops of light, with the Nikon adapter 1 stop.

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/96884-ada...addiction.html

Pentax has a flange focal distance of 45.46mm. The only major mounts with a flange focal distance longer than the K-mount are Nikon F, Olympus OM, and Leica R. Contax C/Y has the same flange distance and can be made to fit with some modification.

Canon FD has a flange distance of 42mm. M4/3 has a flange distance of 19.25mm, Sony E-mount is 18mm, that is why there are adapters for every SLR lens mount available for those mounts.


Last edited by boriscleto; 01-21-2013 at 06:49 PM.
01-21-2013, 06:49 PM   #9
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Thanks for the info. I appreciate it.
01-24-2013, 03:54 PM   #10
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Actually, IF you can adjust the helicoid for infinity focus, you should be able to adapt it to K-mount no problem.

It is going to be lens specific though AND you would need to physically replace the mount to be able to even possibly get infinity focus as the FD register distance is 3.46mm shorter than the Pentax register distance.

I have done this with a Konica 58mm 1.4 lens and was able to get infinity focus on my K10d. With the K-01 it would have been easier becaue I would not have had to file away at the ring that hold in the rear piece of glass in order to clear the mirror.

It is not possible with an adapter, but with physically modifying the lens, it may be possible.

BTW, flanged M42 to K mount adapters work great as replacement mounts for converting lenses.

After looking at the register distance chart again, it really looks to me like FD lenses should be easier to convert than Konica lenses. The Konica lenses have an almost 5mm register distance difference compared to the "only" 3.46mm register distance difference of the FD lenses.

http://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html

Last edited by cyclone3d; 01-24-2013 at 03:59 PM. Reason: add info
01-24-2013, 04:03 PM   #11
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There is a thread that discusses all adaptors that can be used to mount various things to Pentax K mount bodies

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/96884-ada...addiction.html

Just for info, I have a Nikon to PK and Canon FD to PK adaptors, the Nikon adaptor has a 1.25 magnification and the canon has a 1.45 magnification to sort out infinity focus. Wide open on cheap lenses these adaptors produce a lot of softness and bleeding of colors at edges, but stopped down they are not too bad. The bigger issue is the internal infinity focus elements add focal length, so they are really only suitable for tele lenses
01-24-2013, 04:38 PM   #12
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QuoteOriginally posted by Lowell Goudge Quote
There is a thread that discusses all adaptors that can be used to mount various things to Pentax K mount bodies

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/96884-ada...addiction.html

Just for info, I have a Nikon to PK and Canon FD to PK adaptors, the Nikon adaptor has a 1.25 magnification and the canon has a 1.45 magnification to sort out infinity focus. Wide open on cheap lenses these adaptors produce a lot of softness and bleeding of colors at edges, but stopped down they are not too bad. The bigger issue is the internal infinity focus elements add focal length, so they are really only suitable for tele lenses
I think I said all that

https://www.pentaxforums.com/forums/pentax-k-01/212701-fd-lens-k-01-without-g...ml#post2249438
01-24-2013, 06:37 PM   #13
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QuoteOriginally posted by cyclone3d Quote
Actually, IF you can adjust the helicoid for infinity focus, you should be able to adapt it to K-mount no problem.

It is going to be lens specific though AND you would need to physically replace the mount to be able to even possibly get infinity focus as the FD register distance is 3.46mm shorter than the Pentax register distance.

I have done this with a Konica 58mm 1.4 lens and was able to get infinity focus on my K10d. With the K-01 it would have been easier becaue I would not have had to file away at the ring that hold in the rear piece of glass in order to clear the mirror.

It is not possible with an adapter, but with physically modifying the lens, it may be possible.

BTW, flanged M42 to K mount adapters work great as replacement mounts for converting lenses.

After looking at the register distance chart again, it really looks to me like FD lenses should be easier to convert than Konica lenses. The Konica lenses have an almost 5mm register distance difference compared to the "only" 3.46mm register distance difference of the FD lenses.

Camera Mounts Sorted by Register

Interesting - thank you. I have an 50mm/ 1.8 I dont care for or need that I could test with first.
01-24-2013, 06:39 PM   #14
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Thank you as well boriscleto and lowell
01-24-2013, 07:35 PM   #15
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The longer tele FD lenses like the 400/4.5 can be (relatively) easily converted to a K mount flange once you take off the FD mount & associated parts. It's amazing how much space (thickness) the FD mount takes up! Really complicated linkage the FD is .. so the hardest part is linking up the aperture ring back to work the iris.

Kudos to Canon for switching to EOS years ago & for making excellent manual telephotos available for cheap!
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