Screw mount to K mount adaptor?

Wolf74 · 02-05-2008, 09:12 PM

Hey guys, I was interested in getting a Pentax/Asahi lens for my z-xm. I was wondering if I got the adapter to turn the screw mount to a k-mount would all my meters work? If not then do you guys have any other suggestions as far as getting a manual f1/4 lens? Thanks!

**Canada_Rockies** · 02-05-2008, 09:15 PM

Originally posted by Wolf74

Hey guys, I was interested in getting a Pentax/Asahi lens for my z-xm. I was wondering if I got the adapter to turn the screw mount to a k-mount would all my meters work? If not then do you guys have any other suggestions as far as getting a manual f1/4 lens? Thanks!

The metering will work. The automatic stop down of the aperture will not. You will be using stop down metering with the M42 lens, as there is no way for the camera to hold the aperture open for metering. When you set the lens to f/8, that's what you will see through the viewfinder,, just as if you used the depth of field preview. Annoyingly enough, the M42 lens will probably work in aperture priority AE, whereas the M series lenses will not.

Wolf74 · 02-05-2008, 09:36 PM

Thanks for the info. But I'm not quite sure what you mean by stop down metering. Can ya explain a little?

VF-19 · 02-05-2008, 09:43 PM

Originally posted by Wolf74

Thanks for the info. But I'm not quite sure what you mean by stop down metering. Can ya explain a little?

It simply means that in order for you to get a correct light meter reading, you have to manually set the lens to f8. On the K mount there's a little lever that interacts with a lever in the body that tells the body that the lens is set to f8, on a M42 lens there's no such interaction, so you have to set the lens to what you want, which cuts down on the light going to the light meter.

**Canada_Rockies** · 02-06-2008, 01:15 PM

Originally posted by Wolf74

Thanks for the info. But I'm not quite sure what you mean by stop down metering. Can ya explain a little?

Sorry for the delay - I was off line.

Stop down metering is an expression that means that you meter the exposure with the aperture actually at the setting you will use.

Suppose you have a 55/1.8 M42 lens on your dSLR. When you turn the aperture ring to f/11, the viewfinder will get dark; the aperture blades will actually take the f/11 position. In photo parlance, the lens is "stopped down". The mechancial connection is not there for the M42 lenses on a K mount camera, so the camera has no idea what the f/stop is set to.

The previous post said basically the same as the above. I just used some different words to perhaps help you understand the concept.

Wolf74 · 04-06-2008, 11:02 PM

Thanks again for all your help.

titrisol · 04-07-2008, 06:13 AM

Beware of what adapter you buy
make sure it can focus to INFINITY, a few of them will not work

Peter Zack · 04-07-2008, 06:45 AM

If you are interested in an original Pentax K mount to M42 adapter, I have one I'll sell. Just send me a private message and I'll tell you how to use it as well.

noblepa · 04-07-2008, 07:46 AM

Originally posted by titrisol

Beware of what adapter you buy
make sure it can focus to INFINITY, a few of them will not work

To elaborate on this, some adapters have a large-ish flange that sits outside the lens mount. This added thickness prevents the lens from focusing at infinity. This may be okay if you are doing macro work, but it is not good for general photography.

The genuine Pentax adapter and the better third-party adapters fit entirely inside the camera lens mount opening, leaving a flush surface. Therefore, these adapters allow the lenses to focus to infinity normally.

I'm not very familiar with the ZX-M, but I did have its contemporary, the ZX-60, for a while. The ZX-60 will not function with any lens that does not have an "A" aperture setting, or with a lens that has the aperture set anywhere other than "A". This is not the A-M setting on screw-mount lenses.

If the ZX-M requuires the "A" setting on the aperture, the way the ZX-60 does, then you won't be able to use an adapter, because no screw-mount lens will have the setting.

Paul Noble

Peter Zack · 04-07-2008, 08:02 AM

Paul I'm fairly certain the ZX-M will work as seen in this chart:
The Pentax Camera Lens Compatibility Chart

The adapter with the flange is the following one:
https://www.pentaxforums.com/forums/attachments/pentax-slr-lens-discussion/66...-k-mount-2.jpg
https://www.pentaxforums.com/forums/attachments/pentax-slr-lens-discussion/66...-k-mount-1.jpg

02-05-2008, 09:12 PM	#1
Wolf74 New Member Join Date: Dec 2007 Location: California Posts: 8	Screw mount to K mount adaptor? Hey guys, I was interested in getting a Pentax/Asahi lens for my z-xm. I was wondering if I got the adapter to turn the screw mount to a k-mount would all my meters work? If not then do you guys have any other suggestions as far as getting a manual f1/4 lens? Thanks!

04-07-2008, 07:46 AM	#9
noblepa Veteran Member Join Date: Sep 2007 Location: Bay Village, Ohio USA Posts: 1,142	M42 adapters Originally posted by titrisol Beware of what adapter you buy make sure it can focus to INFINITY, a few of them will not work To elaborate on this, some adapters have a large-ish flange that sits outside the lens mount. This added thickness prevents the lens from focusing at infinity. This may be okay if you are doing macro work, but it is not good for general photography. The genuine Pentax adapter and the better third-party adapters fit entirely inside the camera lens mount opening, leaving a flush surface. Therefore, these adapters allow the lenses to focus to infinity normally. I'm not very familiar with the ZX-M, but I did have its contemporary, the ZX-60, for a while. The ZX-60 will not function with any lens that does not have an "A" aperture setting, or with a lens that has the aperture set anywhere other than "A". This is not the A-M setting on screw-mount lenses. If the ZX-M requuires the "A" setting on the aperture, the way the ZX-60 does, then you won't be able to use an adapter, because no screw-mount lens will have the setting. Paul Noble

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
For Sale - Sold: Asahi Pentax Screw Mount Reverse Adaptor (Collectors Item) (Worldwide)	oneill	Sold Items	0	03-27-2010 11:35 AM
Pentax Screw mount to K mount adaptor	Sparkle	Pentax SLR Lens Discussion	2	04-14-2009 06:16 PM
Takumar 200mm; Screw mount adaptor??	rdrum76	Pentax SLR Lens Discussion	7	11-13-2007 04:22 PM
For Sale - Sold: FA: Original PENTAX Screw Mount to K Mount Adapter M42	HogRider	Sold Items	0	10-21-2007 02:12 PM

02-05-2008, 09:15 PM	#2
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	Originally posted by Wolf74 Hey guys, I was interested in getting a Pentax/Asahi lens for my z-xm. I was wondering if I got the adapter to turn the screw mount to a k-mount would all my meters work? If not then do you guys have any other suggestions as far as getting a manual f1/4 lens? Thanks! The metering will work. The automatic stop down of the aperture will not. You will be using stop down metering with the M42 lens, as there is no way for the camera to hold the aperture open for metering. When you set the lens to f/8, that's what you will see through the viewfinder,, just as if you used the depth of field preview. Annoyingly enough, the M42 lens will probably work in aperture priority AE, whereas the M series lenses will not.

02-05-2008, 09:36 PM	#3
Wolf74 New Member Join Date: Dec 2007 Location: California Posts: 8 Original Poster	Thanks for the info. But I'm not quite sure what you mean by stop down metering. Can ya explain a little?

02-05-2008, 09:43 PM	#4
VF-19 Veteran Member Join Date: Aug 2007 Location: Ottawa Posts: 364	Originally posted by Wolf74 Thanks for the info. But I'm not quite sure what you mean by stop down metering. Can ya explain a little? It simply means that in order for you to get a correct light meter reading, you have to manually set the lens to f8. On the K mount there's a little lever that interacts with a lever in the body that tells the body that the lens is set to f8, on a M42 lens there's no such interaction, so you have to set the lens to what you want, which cuts down on the light going to the light meter.

02-06-2008, 01:15 PM	#5
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	Originally posted by Wolf74 Thanks for the info. But I'm not quite sure what you mean by stop down metering. Can ya explain a little? Sorry for the delay - I was off line. Stop down metering is an expression that means that you meter the exposure with the aperture actually at the setting you will use. Suppose you have a 55/1.8 M42 lens on your dSLR. When you turn the aperture ring to f/11, the viewfinder will get dark; the aperture blades will actually take the f/11 position. In photo parlance, the lens is "stopped down". The mechancial connection is not there for the M42 lenses on a K mount camera, so the camera has no idea what the f/stop is set to. The previous post said basically the same as the above. I just used some different words to perhaps help you understand the concept.

04-06-2008, 11:02 PM	#6
Wolf74 New Member Join Date: Dec 2007 Location: California Posts: 8 Original Poster	Thanks again for all your help.

04-07-2008, 06:13 AM	#7
titrisol Pentaxian Join Date: Dec 2007 Location: In the most populated state... state of denial Photos: Gallery \| Albums Posts: 1,852	Beware of what adapter you buy make sure it can focus to INFINITY, a few of them will not work

04-07-2008, 06:45 AM	#8
Peter Zack Pentaxian Moderator Emeritus Join Date: May 2007 Location: Edmonton Alberta, Canada Photos: Gallery \| Albums Posts: 10,643	If you are interested in an original Pentax K mount to M42 adapter, I have one I'll sell. Just send me a private message and I'll tell you how to use it as well.

04-07-2008, 08:02 AM	#10
Peter Zack Pentaxian Moderator Emeritus Join Date: May 2007 Location: Edmonton Alberta, Canada Photos: Gallery \| Albums Posts: 10,643	Paul I'm fairly certain the ZX-M will work as seen in this chart: The Pentax Camera Lens Compatibility Chart The adapter with the flange is the following one: https://www.pentaxforums.com/forums/attachments/pentax-slr-lens-discussion/66...-k-mount-2.jpg https://www.pentaxforums.com/forums/attachments/pentax-slr-lens-discussion/66...-k-mount-1.jpg