Anyone here ever converted K mount to F mount and retained full functionality?

Nass · 08-11-2018, 02:18 PM

As the question says - anyone done this?

Thanks

**TwoUptons** · 08-11-2018, 02:31 PM

I think you need more detail there...

I have some T4 lenses that can go back and forth with ease, for example, but I don’t know of anyone who has ended up with full functionality from a DA lens converted to F mount...

-Eric

**PJ1** · 08-11-2018, 02:38 PM

I suspect that even if the electrical contacts lined up identically, the camera body might not be able to communicate with the lens properly. It could be "garbage in, garbage out"' But it would be interesting to know the answer.

torashi · 08-11-2018, 03:29 PM

If the design of the lens allows for it, sure. And I only know of third party lenses that can be converted by the manufacturer from one mount to the other. And then there are the manual focus Tamron Adaptall lenses.

thazooo · 08-11-2018, 03:31 PM - **1 Like**

Probably not. Years ago there was a guy shooting old Nikon lenses on Pentax digi. Had a gallery on Pbase and everything. IIRC Lens didn't fully mount, no infinity focus, manual aperture only. It was an interesting read.

**boriscleto** · 08-11-2018, 03:51 PM - **2 Likes**

The focal flange distance is what makes it something nobody is going to bother with. F mount to K mount is so much easier. Nikon F and Leica R are really universal donor lenses...

solitudebound · 08-11-2018, 04:05 PM

According to Sigma it's more trouble to convert a lens to a Pentax K-mount. I know when i sent in a lens to get the different mount installed they got agitated when i chose Pentax. Considering that i was paying for it and the shipping it was a strange experience. I know that people have had problems with the Sigma 18-35 Art on the K-3 with not communicating with the camera intermittently. I suspect the conversion to F-mount would have similar problems.

**UncleVanya** · 08-11-2018, 04:26 PM

Originally posted by thazooo

Probably not. Years ago there was a guy shooting old Nikon lenses on Pentax digi. Had a gallery on Pbase and everything. IIRC Lens didn't fully mount, no infinity focus, manual aperture only. It was an interesting read.

Nikon mounts on Pentax and gives BEYOND infinity focus - the mount for Pentax is shorter than Nikon slightly. You can shim to make it exact but even without shimming you have infinity focus. The lens will not lock unless you drill a small recess in the position of the pentax lock and it will only turn about a quarter of a turn. It is fine for light small lenses but I wouldn't put a large telephoto on it. You can also use a flanged m42 adapter on some nikons by removing the lens mount and remounting onto the m42 adapter to give a full K mount. No aperture control and no electronics of course.

**Rondec** · 08-11-2018, 06:25 PM

Originally posted by solitudebound

According to Sigma it's more trouble to convert a lens to a Pentax K-mount. I know when i sent in a lens to get the different mount installed they got agitated when i chose Pentax. Considering that i was paying for it and the shipping it was a strange experience. I know that people have had problems with the Sigma 18-35 Art on the K-3 with not communicating with the camera intermittently. I suspect the conversion to F-mount would have similar problems.

I think that was in the past when Pentax was still using a mechanical aperture lever. Now that they have Kaf 4 cameras that don't need lenses with a mechanical aperture lever I don't think it is any harder to make k mount lenses than for any other mount. The bigger issue for Sigma is that they don't sell very many Pentax mount lenses compared to other brands and so it isn't worth it to them to make them.

reh321 · 08-11-2018, 06:32 PM

Originally posted by Rondec

I think that was in the past when Pentax was still using a mechanical aperture lever. Now that they have Kaf 4 cameras that don't need lenses with a mechanical aperture lever I don't think it is any harder to make k mount lenses than for any other mount. The bigger issue for Sigma is that they don't sell very many Pentax mount lenses compared to other brands and so it isn't worth it to them to make them.

Are KAF4 specs publicly available?? You would have to know exactly how to signal what.

reh321 · 08-11-2018, 06:41 PM

Originally posted by boriscleto

The focal flange distance is what makes it something nobody is going to bother with. F mount to K mount is so much easier. Nikon F and Leica R are really universal donor lenses...

Are you sure about that?

The table I have says Nikon F is 46.50 mm while K-mount is 45.46mm

A 1.04mm spacer would convert K-mount to F-mount.
A "-1.04mm spacer" would be needed to convert F-mount to K-mount

**UncleVanya** · 08-11-2018, 06:47 PM

Originally posted by reh321

Are you sure about that?

The table I have says Nikon F is 46.50 mm while K-mount is 45.46mm

A 1.04mm spacer would convert K-mount to F-mount.
A "-1.04mm spacer" would be needed to convert F-mount to K-mount

You.misunderstand. a k mount needs to be 45.46 from the sensor. Put it on a Nikon it is too far and loses infinity. Nikon on Pentax needs a 1.04mm additional spacer to get the exact infinity focus. But even without a spacer it will focus to infinity earlier than infinity is marked.

reh321 · 08-11-2018, 07:08 PM

Originally posted by UncleVanya

You.misunderstand. a k mount needs to be 45.46 from the sensor. Put it on a Nikon it is too far and loses infinity. Nikon on Pentax needs a 1.04mm additional spacer to get the exact infinity focus. But even without a spacer it will focus to infinity earlier than infinity is marked.

OK, I was confusing this with another question - what it would take to use my M42 lenses on the Metabones F-to-Q adapter. Nikon experts tell me it wouldn't be worthwhile .... I guess 1.04mm thick adapters don't exist, which is why M42-mount to F-mount adapters require glass.

**UncleVanya** · 08-11-2018, 07:36 PM

Originally posted by reh321

OK, I was confusing this with another question - what it would take to use my M42 lenses on the Metabones F-to-Q adapter. Nikon experts tell me it wouldn't be worthwhile .... I guess 1.04mm thick adapters don't exist, which is why M42-mount to F-mount adapters require glass.

An F to Q adapter holds the lens at the extra long distance needed for an F mount from the sensor which means the M42 lens will not focus at infinity. If you had a K to Q adapter and mounted a Nikon to it then you could focus to infinity but you would get there early unless you shimmed it. Your MFD might be reduced if you don't shim it.

To recap. A lens with shorter registration distance can't be mounted onto a mount or an adapter with a longer registration distance without optical glass that is acting like a teleconverter. Additionally lenses that are too close in registration distance are typically hard to mount because the size of the adapter is too thin to be viable. NIkon on Pentax without an adapter or with an changed lens plate is viable but only just. Lenses that require a longer distance and are sufficiently different to allow for a spacer adapter can be mounted which is why mirrorless cameras with very short registration distances can mount just about any lens by adding a spacer type adapter.

Incidentally there are people who use the Takumar M42 50mm macro on Nikon without an optical glass adapter - they do so only for macro not for infinity focus.

Nass · 08-11-2018, 11:57 PM - **1 Like**

The reason I asked - www.photomacrography.net :: View topic - How to convert a Pentax K-1 to Nikon mount

A fellow on another forum removed the K mount on a K1 and put on a Nikon mount.

He wanted K1 for pixel shift, this is a specialist extreme macro forum I participate in.

Very brave, and I wondered if anyone here had done it!

Cheers

08-11-2018, 02:18 PM	#1
Nass Veteran Member Join Date: Aug 2009 Location: The British Isles Photos: Gallery Posts: 2,402	Anyone here ever converted K mount to F mount and retained full functionality? As the question says - anyone done this? Thanks

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08-11-2018, 02:31 PM	#2
TwoUptons Loyal Site Supporter Join Date: Nov 2015 Photos: Albums Posts: 4,213	I think you need more detail there... I have some T4 lenses that can go back and forth with ease, for example, but I don’t know of anyone who has ended up with full functionality from a DA lens converted to F mount... -Eric

08-11-2018, 02:38 PM	#3
PJ1 Loyal Site Supporter Join Date: Jul 2012 Location: Toowoomba, Australia Photos: Gallery \| Albums Posts: 5,484	I suspect that even if the electrical contacts lined up identically, the camera body might not be able to communicate with the lens properly. It could be "garbage in, garbage out"' But it would be interesting to know the answer.

08-11-2018, 03:29 PM	#4
torashi Veteran Member Join Date: Sep 2017 Location: Medellín Posts: 1,322	If the design of the lens allows for it, sure. And I only know of third party lenses that can be converted by the manufacturer from one mount to the other. And then there are the manual focus Tamron Adaptall lenses.

08-11-2018, 03:31 PM - 1 Like	#5
thazooo Pentaxian Join Date: Sep 2006 Location: Mississippi, USA Photos: Gallery Posts: 854	Probably not. Years ago there was a guy shooting old Nikon lenses on Pentax digi. Had a gallery on Pbase and everything. IIRC Lens didn't fully mount, no infinity focus, manual aperture only. It was an interesting read.

08-11-2018, 03:51 PM - 2 Likes	#6
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	The focal flange distance is what makes it something nobody is going to bother with. F mount to K mount is so much easier. Nikon F and Leica R are really universal donor lenses...

08-11-2018, 04:05 PM	#7
solitudebound Senior Member Join Date: Oct 2017 Posts: 140	According to Sigma it's more trouble to convert a lens to a Pentax K-mount. I know when i sent in a lens to get the different mount installed they got agitated when i chose Pentax. Considering that i was paying for it and the shipping it was a strange experience. I know that people have had problems with the Sigma 18-35 Art on the K-3 with not communicating with the camera intermittently. I suspect the conversion to F-mount would have similar problems.

08-11-2018, 04:26 PM	#8
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,400	Originally posted by thazooo Probably not. Years ago there was a guy shooting old Nikon lenses on Pentax digi. Had a gallery on Pbase and everything. IIRC Lens didn't fully mount, no infinity focus, manual aperture only. It was an interesting read. Nikon mounts on Pentax and gives BEYOND infinity focus - the mount for Pentax is shorter than Nikon slightly. You can shim to make it exact but even without shimming you have infinity focus. The lens will not lock unless you drill a small recess in the position of the pentax lock and it will only turn about a quarter of a turn. It is fine for light small lenses but I wouldn't put a large telephoto on it. You can also use a flanged m42 adapter on some nikons by removing the lens mount and remounting onto the m42 adapter to give a full K mount. No aperture control and no electronics of course.

08-11-2018, 06:25 PM	#9
Rondec Loyal Site Supporter Join Date: Mar 2009 Location: Gladys, Virginia Photos: Gallery Posts: 27,652	Originally posted by solitudebound According to Sigma it's more trouble to convert a lens to a Pentax K-mount. I know when i sent in a lens to get the different mount installed they got agitated when i chose Pentax. Considering that i was paying for it and the shipping it was a strange experience. I know that people have had problems with the Sigma 18-35 Art on the K-3 with not communicating with the camera intermittently. I suspect the conversion to F-mount would have similar problems. I think that was in the past when Pentax was still using a mechanical aperture lever. Now that they have Kaf 4 cameras that don't need lenses with a mechanical aperture lever I don't think it is any harder to make k mount lenses than for any other mount. The bigger issue for Sigma is that they don't sell very many Pentax mount lenses compared to other brands and so it isn't worth it to them to make them.

08-11-2018, 06:32 PM	#10
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,177	Originally posted by Rondec I think that was in the past when Pentax was still using a mechanical aperture lever. Now that they have Kaf 4 cameras that don't need lenses with a mechanical aperture lever I don't think it is any harder to make k mount lenses than for any other mount. The bigger issue for Sigma is that they don't sell very many Pentax mount lenses compared to other brands and so it isn't worth it to them to make them. Are KAF4 specs publicly available?? You would have to know exactly how to signal what.

08-11-2018, 06:41 PM	#11
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,177	Originally posted by boriscleto The focal flange distance is what makes it something nobody is going to bother with. F mount to K mount is so much easier. Nikon F and Leica R are really universal donor lenses... Are you sure about that? The table I have says Nikon F is 46.50 mm while K-mount is 45.46mm A 1.04mm spacer would convert K-mount to F-mount. A "-1.04mm spacer" would be needed to convert F-mount to K-mount

08-11-2018, 06:47 PM	#12
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,400	Originally posted by reh321 Are you sure about that? The table I have says Nikon F is 46.50 mm while K-mount is 45.46mm A 1.04mm spacer would convert K-mount to F-mount. A "-1.04mm spacer" would be needed to convert F-mount to K-mount You.misunderstand. a k mount needs to be 45.46 from the sensor. Put it on a Nikon it is too far and loses infinity. Nikon on Pentax needs a 1.04mm additional spacer to get the exact infinity focus. But even without a spacer it will focus to infinity earlier than infinity is marked.

08-11-2018, 07:08 PM	#13
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,177	Originally posted by UncleVanya You.misunderstand. a k mount needs to be 45.46 from the sensor. Put it on a Nikon it is too far and loses infinity. Nikon on Pentax needs a 1.04mm additional spacer to get the exact infinity focus. But even without a spacer it will focus to infinity earlier than infinity is marked. OK, I was confusing this with another question - what it would take to use my M42 lenses on the Metabones F-to-Q adapter. Nikon experts tell me it wouldn't be worthwhile .... I guess 1.04mm thick adapters don't exist, which is why M42-mount to F-mount adapters require glass.

08-11-2018, 07:36 PM	#14
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,400	Originally posted by reh321 OK, I was confusing this with another question - what it would take to use my M42 lenses on the Metabones F-to-Q adapter. Nikon experts tell me it wouldn't be worthwhile .... I guess 1.04mm thick adapters don't exist, which is why M42-mount to F-mount adapters require glass. An F to Q adapter holds the lens at the extra long distance needed for an F mount from the sensor which means the M42 lens will not focus at infinity. If you had a K to Q adapter and mounted a Nikon to it then you could focus to infinity but you would get there early unless you shimmed it. Your MFD might be reduced if you don't shim it. To recap. A lens with shorter registration distance can't be mounted onto a mount or an adapter with a longer registration distance without optical glass that is acting like a teleconverter. Additionally lenses that are too close in registration distance are typically hard to mount because the size of the adapter is too thin to be viable. NIkon on Pentax without an adapter or with an changed lens plate is viable but only just. Lenses that require a longer distance and are sufficiently different to allow for a spacer adapter can be mounted which is why mirrorless cameras with very short registration distances can mount just about any lens by adding a spacer type adapter. Incidentally there are people who use the Takumar M42 50mm macro on Nikon without an optical glass adapter - they do so only for macro not for infinity focus.

08-11-2018, 11:57 PM - 1 Like	#15
Nass Veteran Member Join Date: Aug 2009 Location: The British Isles Photos: Gallery Posts: 2,402 Original Poster	The reason I asked - www.photomacrography.net :: View topic - How to convert a Pentax K-1 to Nikon mount A fellow on another forum removed the K mount on a K1 and put on a Nikon mount. He wanted K1 for pixel shift, this is a specialist extreme macro forum I participate in. Very brave, and I wondered if anyone here had done it! Cheers