adapters for non-K-mount lenses to Pentax K-mount DSLRs: new dimensions for LBA

**Lowell Goudge** · 11-14-2013, 04:33 PM

Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.

Originally posted by tripodquest

thank you for your reply, I was actually looking at canon cameras... this would be another good reason!

It is not that I am a cannon fan, but it is a simple fact, it has the shortest regestry distance of any DSLR and the mount throat is huge, 54mm from what I can see, but still not enough for the lenses you want to. Mount but with a 44mm regestry distance it is short.

The other option is to look at an APS-C mirror less camera with a short regestry, or a micro 4/3 camera. Even pentax Q as they make mounts for almost any lens

tripodquest · 11-14-2013, 05:35 PM

Originally posted by Lowell Goudge

It is not that I am a cannon fan, but it is a simple fact, it has the shortest regestry distance of any DSLR and the mount throat is huge, 54mm from what I can see, but still not enough for the lenses you want to. Mount but with a 44mm regestry distance it is short.

The other option is to look at an APS-C mirror less camera with a short regestry, or a micro 4/3 camera. Even pentax Q as they make mounts for almost any lens

Thanks for the info. But I thought short registry distance was a good thing? If you can fit enough of the rear elements inside the body. I will have to check the exact measurements though. How much larger does the mount throat have to be compared to the original mount in the lens? Another option would be to (let someone with the skills) take out the original mount which would make the read diameter a little smaller, then work a new mount around that so that the distance matches? "54 mm internal" is indeed the diameter of the Canon mount. The Arri bayonet mount has these measurements:
Flange focal distance: 52.00 mm
Diameter: 41.00 mm

The diameter of the mount is 13mm less than the canon, I think it would fit fine?

as long as the lens rear doesn't get too wide in the few mm it would have to be lowered. Arri has other mounts, like the PL 54.00 mm and the PL Maxi 62.00mm, those would be too big, but the smaller mounts should be fine. I'll just have to look for lenses with the smaller mounts.

it also says: PL-mount optional by user choice: Canon EOS C300, Canon EOS C500, Red One, Red Epic, Red Scarlet)
So I think they can be adapted, at least if you ask Arri or someone who knows how to do it? Since it's only the PL mount that's too big, you'd have to remove it and replace it with the right mount and then make sure no light gets through.

c-meier · 11-17-2013, 09:07 AM

Well.. no answer at all from Pentax. I didn't expect much, but a mail would have been nice

foivosloxias · 05-10-2014, 01:02 PM

Great thread, lots of info!
I just bought an adapter "PENTAX K/M CANON", "MADE IN JAPAN", the store told me they had this since the 80's. I already had two FD lenses, a 55mm f1.2 "chrome nose" & a 50mm f1.4 SSC, in excellent condition(almost unused). I tried the 55mm with my Canon A-1 and results were just "good", cause of a really bad negative processing. First shots with the K-x were more than pleasing! My usual prime is a Sigma 50mm 2.8 macro and I was totally satisfied with it but I am really more pleased with the color and contrast from the 50mm f1.4 SSC. You can find some photos here:

~https://www.flickr.com/photos/foivosloxias/sets/72157644551962981

I have a question for the more experienced users, when I input the "focal length" of the lens, in my pentax, do I choose 50/55 or more by multiplying with the 1.2x-14x of the adapter? What is the purpose of this input, is it for the SR?

Last edited by foivosloxias; 05-12-2014 at 10:14 AM.

**boriscleto** · 05-10-2014, 02:16 PM - **1 Like**

Originally posted by foivosloxias

I have a question fro the more experienced users, when I input the "focal length" of the lens, in my pentax, do I choose 50/55 or more by multiplying with the 1.2x-14x of the adapter? What is the purpose of this input, is it for the SR?

Technically you should enter the focal length with the multiplier of the converter (1.4x). So you should enter 70mm for the 50 and 77 for the 55.

foivosloxias · 05-12-2014, 10:13 AM

Originally posted by boriscleto

Technically you should enter the focal length with the multiplier of the converter (1.4x). So you should enter 70mm for the 50 and 77 for the 55.

Thank you for the answer!

**Douglas_of_Sweden** · 08-22-2014, 04:40 PM

Somewhere in the beginning of this thread I noted that someone were selling a topcon to m42 replacement mount on e-bay...and then it dissapeared. It annoyed me a lot since I had been waiting to buy one until I actually had any topcon lens to convert.
Anyway, now there is someone selling a conversion kit again on ebay: M42 Adapter Topcon Exakta Remounting KIT Black OR Silver DIY M42 CAP Included | eBay
In addition, Fotodiox is selling a topcon/exakta to K-mount adapter with optical elements (much like the Canon FD to K-mount adapter dicussed earlier in the thread).
I just received the Fotodiox adapter, which looks very well built. Now I'm just waiting for some topcon lense that are on their way. Since I'm planning to use the topcon lenses on topcon cameras and film as well, I'm not planning to do the conversion, not directly at least.

jcdog2006 · 08-22-2014, 05:02 PM

Originally posted by Douglas_of_Sweden

Somewhere in the beginning of this thread I noted that someone were selling a topcon to m42 replacement mount on e-bay...and then it dissapeared. It annoyed me a lot since I had been waiting to buy one until I actually had any topcon lens to convert.
Anyway, now there is someone selling a conversion kit again on ebay: M42 Adapter Topcon Exakta Remounting KIT Black OR Silver DIY M42 CAP Included | eBay
In addition, Fotodiox is selling a topcon/exakta to K-mount adapter with optical elements (much like the Canon FD to K-mount adapter dicussed earlier in the thread).
I just received the Fotodiox adapter, which looks very well built. Now I'm just waiting for some topcon lense that are on their way. Since I'm planning to use the topcon lenses on topcon cameras and film as well, I'm not planning to do the conversion, not directly at least.

Is this one or this one you are looking for? I ordered more than 10 of this for myself.

**Douglas_of_Sweden** · 08-23-2014, 12:06 AM

Originally posted by jcdog2006

Is this one or this one you are looking for? I ordered more than 10 of this for myself.

As should be obvious from my post I am not looking for it.

NicoleC · 10-30-2014, 06:28 AM

Has anyone had a chance to play with the Fotodiox adapter yet? I've got some old Canon gear I can't get rid of, so I am looking at the Fotodiox FD to K adapter. (Fotodiox Pro Lens Adapter, Canon FD, FL Lens to Pentax K Camera Lens Mount Adapter) Fotodiox generally produces some good budget friendly stuff, but I haven't found any test images yet.

AquaDome · 10-30-2014, 09:55 AM

A well-functioning FD-K adapter would make LBA a bit less expensive. Those old FD lenses can be purchased by the pound.

ZombieArmy · 10-30-2014, 12:59 PM

I know this is probably answered somewhere, but for m39 you just use the m39 adapter on a m42 adapter on a kmount camera?

Not a Number · 10-30-2014, 01:21 PM

That works, however the M39 adapter ring I have (I think it was from Fotodiox) doesn't thread into my genuine Pentax (Philippines) M42 adapter. It fits fine in a generic Minolta MD to M42 adapter and directly into my Pentax Auto Bellows (screwmount).

aliasant · 10-31-2014, 11:01 AM

Originally posted by AquaDome

A well-functioning FD-K adapter would make LBA a bit less expensive. Those old FD lenses can be purchased by the pound.

Unfortunatly that isnt really possible without glass in the adapter.
I worked around that by building my own conversion. Those FD lenses are great!
Here are images shot using various FD lenses on my Pentax dslr ( K5 and K3)
Unfortunatly I didnt get the lens names to display correctly.
All Canon FDn lenses - Martin Rodensjo Photography

Jean Poitiers · 11-01-2014, 07:00 AM

OK ... Just FYI here.

Normally you cannot easily mount a Mamiya M42 lens on a PK camera due to the protruding flange of the aperture ring. But if you use a flanged M42 to PK Chinese adapter, it will fit snugly right into the mount space area after you remove/"Dremel off" the aperture control pin/knob found on the base of the Mamiya mount ...

Here's what the final product looks like and it will far focus to about ten(+) feet depending upon aperture used. (xpost info)

A wide open test snap at near MFD ...

11-14-2013, 05:35 PM	#137
tripodquest Inactive Account Join Date: Oct 2013 Posts: 249	Originally posted by Lowell Goudge It is not that I am a cannon fan, but it is a simple fact, it has the shortest regestry distance of any DSLR and the mount throat is huge, 54mm from what I can see, but still not enough for the lenses you want to. Mount but with a 44mm regestry distance it is short. The other option is to look at an APS-C mirror less camera with a short regestry, or a micro 4/3 camera. Even pentax Q as they make mounts for almost any lens Thanks for the info. But I thought short registry distance was a good thing? If you can fit enough of the rear elements inside the body. I will have to check the exact measurements though. How much larger does the mount throat have to be compared to the original mount in the lens? Another option would be to (let someone with the skills) take out the original mount which would make the read diameter a little smaller, then work a new mount around that so that the distance matches? "54 mm internal" is indeed the diameter of the Canon mount. The Arri bayonet mount has these measurements: Flange focal distance: 52.00 mm Diameter: 41.00 mm The diameter of the mount is 13mm less than the canon, I think it would fit fine? as long as the lens rear doesn't get too wide in the few mm it would have to be lowered. Arri has other mounts, like the PL 54.00 mm and the PL Maxi 62.00mm, those would be too big, but the smaller mounts should be fine. I'll just have to look for lenses with the smaller mounts. it also says: PL-mount optional by user choice: Canon EOS C300, Canon EOS C500, Red One, Red Epic, Red Scarlet) So I think they can be adapted, at least if you ask Arri or someone who knows how to do it? Since it's only the PL mount that's too big, you'd have to remove it and replace it with the right mount and then make sure no light gets through. Last edited by tripodquest; 11-14-2013 at 05:40 PM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Lens mount adapters	macdaddy	Pentax Camera and Field Accessories	10	08-24-2010 09:20 AM
Screw to K mount adapters	wildman	Pentax SLR Lens Discussion	59	01-12-2009 08:47 PM
For Sale - Sold: T-Mount and M42 Adapters	dazedgonebye	Sold Items	4	02-08-2008 02:36 PM
Question Regarding T-Mount Adapters	Mikhail	Pentax Camera and Field Accessories	4	01-30-2008 07:56 AM

11-14-2013, 04:33 PM	#136
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,888	Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. Originally posted by tripodquest thank you for your reply, I was actually looking at canon cameras... this would be another good reason! It is not that I am a cannon fan, but it is a simple fact, it has the shortest regestry distance of any DSLR and the mount throat is huge, 54mm from what I can see, but still not enough for the lenses you want to. Mount but with a 44mm regestry distance it is short. The other option is to look at an APS-C mirror less camera with a short regestry, or a micro 4/3 camera. Even pentax Q as they make mounts for almost any lens

11-17-2013, 09:07 AM	#138
c-meier Senior Member Join Date: Apr 2012 Location: Concepción, Chile Posts: 128	Well.. no answer at all from Pentax. I didn't expect much, but a mail would have been nice

05-10-2014, 01:02 PM	#139
foivosloxias Junior Member Join Date: Dec 2009 Photos: Gallery \| Albums Posts: 25	Great thread, lots of info! I just bought an adapter "PENTAX K/M CANON", "MADE IN JAPAN", the store told me they had this since the 80's. I already had two FD lenses, a 55mm f1.2 "chrome nose" & a 50mm f1.4 SSC, in excellent condition(almost unused). I tried the 55mm with my Canon A-1 and results were just "good", cause of a really bad negative processing. First shots with the K-x were more than pleasing! My usual prime is a Sigma 50mm 2.8 macro and I was totally satisfied with it but I am really more pleased with the color and contrast from the 50mm f1.4 SSC. You can find some photos here: ~https://www.flickr.com/photos/foivosloxias/sets/72157644551962981 I have a question for the more experienced users, when I input the "focal length" of the lens, in my pentax, do I choose 50/55 or more by multiplying with the 1.2x-14x of the adapter? What is the purpose of this input, is it for the SR? Last edited by foivosloxias; 05-12-2014 at 10:14 AM.

05-10-2014, 02:16 PM - 1 Like	#140
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Originally posted by foivosloxias I have a question fro the more experienced users, when I input the "focal length" of the lens, in my pentax, do I choose 50/55 or more by multiplying with the 1.2x-14x of the adapter? What is the purpose of this input, is it for the SR? Technically you should enter the focal length with the multiplier of the converter (1.4x). So you should enter 70mm for the 50 and 77 for the 55.

05-12-2014, 10:13 AM	#141
foivosloxias Junior Member Join Date: Dec 2009 Photos: Gallery \| Albums Posts: 25	Originally posted by boriscleto Technically you should enter the focal length with the multiplier of the converter (1.4x). So you should enter 70mm for the 50 and 77 for the 55. Thank you for the answer!

08-22-2014, 04:40 PM	#142
Douglas_of_Sweden Site Supporter Join Date: Apr 2008 Location: Stockholm Photos: Gallery Posts: 3,374 Original Poster	Somewhere in the beginning of this thread I noted that someone were selling a topcon to m42 replacement mount on e-bay...and then it dissapeared. It annoyed me a lot since I had been waiting to buy one until I actually had any topcon lens to convert. Anyway, now there is someone selling a conversion kit again on ebay: M42 Adapter Topcon Exakta Remounting KIT Black OR Silver DIY M42 CAP Included \| eBay In addition, Fotodiox is selling a topcon/exakta to K-mount adapter with optical elements (much like the Canon FD to K-mount adapter dicussed earlier in the thread). I just received the Fotodiox adapter, which looks very well built. Now I'm just waiting for some topcon lense that are on their way. Since I'm planning to use the topcon lenses on topcon cameras and film as well, I'm not planning to do the conversion, not directly at least.

08-22-2014, 05:02 PM	#143
jcdog2006 Pentaxian Join Date: Aug 2009 Location: San Francisco Bay Area, CA Posts: 310	Originally posted by Douglas_of_Sweden Somewhere in the beginning of this thread I noted that someone were selling a topcon to m42 replacement mount on e-bay...and then it dissapeared. It annoyed me a lot since I had been waiting to buy one until I actually had any topcon lens to convert. Anyway, now there is someone selling a conversion kit again on ebay: M42 Adapter Topcon Exakta Remounting KIT Black OR Silver DIY M42 CAP Included \| eBay In addition, Fotodiox is selling a topcon/exakta to K-mount adapter with optical elements (much like the Canon FD to K-mount adapter dicussed earlier in the thread). I just received the Fotodiox adapter, which looks very well built. Now I'm just waiting for some topcon lense that are on their way. Since I'm planning to use the topcon lenses on topcon cameras and film as well, I'm not planning to do the conversion, not directly at least. Is this one or this one you are looking for? I ordered more than 10 of this for myself.

08-23-2014, 12:06 AM	#144
Douglas_of_Sweden Site Supporter Join Date: Apr 2008 Location: Stockholm Photos: Gallery Posts: 3,374 Original Poster	Originally posted by jcdog2006 Is this one or this one you are looking for? I ordered more than 10 of this for myself. As should be obvious from my post I am not looking for it.

10-30-2014, 06:28 AM	#145
NicoleC Veteran Member Join Date: Oct 2013 Location: Madison, AL Posts: 448	Has anyone had a chance to play with the Fotodiox adapter yet? I've got some old Canon gear I can't get rid of, so I am looking at the Fotodiox FD to K adapter. (Fotodiox Pro Lens Adapter, Canon FD, FL Lens to Pentax K Camera Lens Mount Adapter) Fotodiox generally produces some good budget friendly stuff, but I haven't found any test images yet.

10-30-2014, 09:55 AM	#146
AquaDome Veteran Member Join Date: Jan 2014 Location: New Carlisle, IN Photos: Gallery \| Albums Posts: 1,475	A well-functioning FD-K adapter would make LBA a bit less expensive. Those old FD lenses can be purchased by the pound.

10-30-2014, 12:59 PM	#147
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210	I know this is probably answered somewhere, but for m39 you just use the m39 adapter on a m42 adapter on a kmount camera?

10-30-2014, 01:21 PM	#148
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	That works, however the M39 adapter ring I have (I think it was from Fotodiox) doesn't thread into my genuine Pentax (Philippines) M42 adapter. It fits fine in a generic Minolta MD to M42 adapter and directly into my Pentax Auto Bellows (screwmount).

10-31-2014, 11:01 AM	#149
aliasant Veteran Member Join Date: Feb 2010 Location: Stockholm Photos: Gallery \| Albums Posts: 634	Originally posted by AquaDome A well-functioning FD-K adapter would make LBA a bit less expensive. Those old FD lenses can be purchased by the pound. Unfortunatly that isnt really possible without glass in the adapter. I worked around that by building my own conversion. Those FD lenses are great! Here are images shot using various FD lenses on my Pentax dslr ( K5 and K3) Unfortunatly I didnt get the lens names to display correctly. All Canon FDn lenses - Martin Rodensjo Photography

11-01-2014, 07:00 AM	#150
Jean Poitiers Pentaxian Join Date: Apr 2011 Location: Lost in translation ... Photos: Gallery \| Albums Posts: 18,076	OK ... Just FYI here. Normally you cannot easily mount a Mamiya M42 lens on a PK camera due to the protruding flange of the aperture ring. But if you use a flanged M42 to PK Chinese adapter, it will fit snugly right into the mount space area after you remove/"Dremel off" the aperture control pin/knob found on the base of the Mamiya mount ... Here's what the final product looks like and it will far focus to about ten(+) feet depending upon aperture used. (xpost info) A wide open test snap at near MFD ...