Pentax brand M42 adapter

BAB · 02-04-2015, 12:13 PM

Hi,

I recently bought a mint SMC Takumar 35/3.5 as a walk-around lens for (excuse me) a used Sony a7 I couldn't resist. The 35/3.5 lives up to its reputation as a super lens! I bought the Pentax version of the Takumar adapter and have now discovered the mount won't come off the PK to Sony E adapter. It appears to be made that way, as the release button won't come out of the adapter ring, although it does allow me to add and remove K mount lenses. Problem is, won't the extra thickness of the screw mount affect the performance of the K mount lenses? Especially as involves vignetting, let alone infinity focus?

Is there a Takumar adapter ring I can buy that will simply allow the adapter ring to be removed along with its Takumar lens?

Thanks,
BAB

**wtlwdwgn** · 02-04-2015, 12:30 PM

The answer to the last question is no. An M42 adapter should be mounted to the camera first and then the lens screwed into the adapter. The lens will begin to unscrew if you attempt to remove both. The Pentax M42 adapter has a spring clip which holds the adapter in place. I just use a finger nail to release the spring to remove the adapter. I wouldn't try to use any kind of 'tool' as you might break the spring and it will become permanently stuck.

vonBaloney · 02-04-2015, 12:34 PM

Originally posted by BAB

I recently bought a mint SMC Takumar 35/3.5 as a walk-around lens for (excuse me) a used Sony a7 I couldn't resist. The 35/3.5 lives up to its reputation as a super lens! I bought the Pentax version of the Takumar adapter and have now discovered the mount won't come off the PK to Sony E adapter. It appears to be made that way, as the release button won't come out of the adapter ring, although it does allow me to add and remove K mount lenses. Problem is, won't the extra thickness of the screw mount affect the performance of the K mount lenses? Especially as involves vignetting, let alone infinity focus?

So you're saying your m42 adapter is stuck in the PK/E adapter, but you can still mount K lenses? Sounds potentially dangerous (to the K lenses)...

osv · 02-04-2015, 12:45 PM

Originally posted by BAB

Problem is, won't the extra thickness of the screw mount affect the performance of the K mount lenses? Especially as involves vignetting, let alone infinity focus?

there is no noticeable change in the vignetting, because whatever thicknesses we are talking about here by adding the adapter are tiny to non-existent... remember that a real pentax factory m42 to pk adapter hits infinity focus just about every time on a pentax camera, while the aftermarket m42 to pk adapters don't.

since all cheap nex adapters are deliberately sized to let the lens focus beyond infinity, adding even an aftermarket m42 to pk adapter to the nex adapter still leaves plenty of room for infinity focus... i know because i've done it.

the key to working with nex adapters is to remember that hard infinity focus stops on lenses are an obsolete dslr concept, that doesn't apply here... evf magnification is more accurate than any autofocus system will ever be, if you have time to use it, and even then you still have focus peaking to work with.

BAB · 02-04-2015, 12:46 PM

Originally posted by vonBaloney

So you're saying your m42 adapter is stuck in the PK/E adapter, but you can still mount K lenses? Sounds potentially dangerous (to the K lenses)...

The adapter is designed that way.......it's only the central screw mount portion that is removable, leaving a K-mount adapter that mounts K-mount lenses. It's the extra thickness of the adapter upon which K-mount lenses are mounted that is my chief question. I.e., does not the extra thickness change the performance of the K-mount lens?

BAB

BAB · 02-04-2015, 12:50 PM

Originally posted by wtlwdwgn

The answer to the last question is no. An M42 adapter should be mounted to the camera first and then the lens screwed into the adapter. The lens will begin to unscrew if you attempt to remove both. The Pentax M42 adapter has a spring clip which holds the adapter in place. I just use a finger nail to release the spring to remove the adapter. I wouldn't try to use any kind of 'tool' as you might break the spring and it will become permanently stuck.

Yes, I'm aware of that. But why is there not provision for removing the adapter ring, which was my primary question.......does the extra thickness of the adapter ring change the performance of the K lens mounted on top of it?

Thanks,
BAB

osv · 02-04-2015, 12:51 PM

Originally posted by BAB

does the extra thickness of the adapter ring change the performance of the K lens mounted on top of it?

for the second time... NO

vonBaloney · 02-04-2015, 12:55 PM

Originally posted by BAB

The adapter is designed that way......

Which adapter is designed that way? The Sony/PK adapter? Because any PK/M42 adapter is not designed to have K mount lenses "mounted on top of it" -- makes no sense.

BAB · 02-04-2015, 12:56 PM

Originally posted by dcshooter

Sounds like it might have got pushed off the bayonet and fallen into the Sony adapter. If you remove the screws from the front of the Sony adapter, you shold be able to lift the bayonet out and retrieve your m42 adapter.

No, I don't think that possible. The screwmount portion of the adapter ring is removable ...... an is actually here on my desk top.

---------- Post added 02-04-15 at 12:49 PM ----------

Also, does your m42 to Pentax K adapter look like this:

Type 1 (e.g. the genuine Pentax branded adapter) does not introduce extra thickness, while type #2 does. That one will cause you to lose infinity focus.

The adapter I bought is the original Pentax branded adapter. It's good to know I won't lose infinity focus (difficult to ascertain unless I go outside, and it's 10 degrees and I don't want to go outside

. BUT WHAT ABOUT VIGNETTING?

Thanks for the reply........ BAB

BAB · 02-04-2015, 01:02 PM

Originally posted by vonBaloney

Which adapter is designed that way? The Sony/PK adapter? Because any PK/M42 adapter is not designed to have K mount lenses "mounted on top of it" -- makes no sense.

Um, yes it does, as with the original Pentax adapter (which I didn't know until I mounted the adapter) has a central ring which is removable when clicking a retaining ring. The central ring is an M42 threaded ring. With that ring removed, the adapter is a plain old PK mount ring and one can mount PK lenses to it. My question is, how does the extra thickness of the adapter ring affect the performance of the lens. One respondent has indicated it won't affect infinity focus of K-mount lenses, but what about VIGNETTING?

You might be confused, in that I've mounted the Pentax Takumar adapter to Pentax K to Sony E adapter already on the camera. Sorry for the confusion.

BAB

---------- Post added 02-04-2015 at 03:04 PM ----------

Originally posted by dcshooter

The m42 lenses are designed to provide full coverage of a 35mm film frame when mounted at the appropriate distance from the film plane. This is the same distance the adapter holds it from your sensor, so it shouldn't vignette, even on a full-frame sensor like the A7.

Thanks, but what I meant was vignetting of K lenses, because of the extra thickness now present due to the adapter.

BAB

BAB · 02-04-2015, 01:35 PM

HOLD THE PRESSES !!! The Pentax Takumar adapter fits inside the K-mount. Duh. I have no idea where I got the idea that there was a second ring that mounted on top of the original K-mount. I am NOT going crazy. I just need my eyes examined.

Thanks much for sending me back to the mount to examine the mount with non-paranoid eyes

BAB

vonBaloney · 02-04-2015, 01:59 PM

Originally posted by BAB

HOLD THE PRESSES !!! The Pentax Takumar adapter fits inside the K-mount. Duh. I have no idea where I got the idea that there was a second ring that mounted on top of the original K-mount. I am NOT going crazy. I just need my eyes examined.

Yes, that's right. The adapter IS the ring (and that's all it is), and the adapter itself IS a K-mount. That's why it makes no sense to say you could then mount K-mount lenses on top of it with it installed because its whole purpose is to take a K-mount and turn it into a (narrower) m42 screw mount. There are ones with an extra flange that sticks outside the mount (messing up infinity focus) -- see the pics posted above of the two versions...

Not a Number · 02-04-2015, 02:47 PM

The instruction manual for the genuine Pentax K mount adapter:
http://www.gyes.eu/documents/pentax_mount_adapter_k.pdf

Most of the time you can use your thumbnail instead of a ball-point pen.

Or you can look in most of the manual focus Pentax camera manuals.

**dms** · 02-04-2015, 02:47 PM

If you remove the spring clip the adapter will stay on the lens when you remove it--but it requires a small cross screwdriver to do this--and if not careful the screw head will be stripped--so it cannot be removed.

02-04-2015, 12:13 PM	#1
BAB Forum Member Join Date: Jul 2008 Location: Maine, USA Posts: 66	Pentax brand M42 adapter Hi, I recently bought a mint SMC Takumar 35/3.5 as a walk-around lens for (excuse me) a used Sony a7 I couldn't resist. The 35/3.5 lives up to its reputation as a super lens! I bought the Pentax version of the Takumar adapter and have now discovered the mount won't come off the PK to Sony E adapter. It appears to be made that way, as the release button won't come out of the adapter ring, although it does allow me to add and remove K mount lenses. Problem is, won't the extra thickness of the screw mount affect the performance of the K mount lenses? Especially as involves vignetting, let alone infinity focus? Is there a Takumar adapter ring I can buy that will simply allow the adapter ring to be removed along with its Takumar lens? Thanks, BAB

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02-04-2015, 12:30 PM	#2
wtlwdwgn Site Supporter Join Date: Jan 2007 Location: Billings, MT Photos: Gallery \| Albums Posts: 13,838	The answer to the last question is no. An M42 adapter should be mounted to the camera first and then the lens screwed into the adapter. The lens will begin to unscrew if you attempt to remove both. The Pentax M42 adapter has a spring clip which holds the adapter in place. I just use a finger nail to release the spring to remove the adapter. I wouldn't try to use any kind of 'tool' as you might break the spring and it will become permanently stuck.

02-04-2015, 12:34 PM	#3
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by BAB I recently bought a mint SMC Takumar 35/3.5 as a walk-around lens for (excuse me) a used Sony a7 I couldn't resist. The 35/3.5 lives up to its reputation as a super lens! I bought the Pentax version of the Takumar adapter and have now discovered the mount won't come off the PK to Sony E adapter. It appears to be made that way, as the release button won't come out of the adapter ring, although it does allow me to add and remove K mount lenses. Problem is, won't the extra thickness of the screw mount affect the performance of the K mount lenses? Especially as involves vignetting, let alone infinity focus? So you're saying your m42 adapter is stuck in the PK/E adapter, but you can still mount K lenses? Sounds potentially dangerous (to the K lenses)...

02-04-2015, 12:45 PM	#4
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	Originally posted by BAB Problem is, won't the extra thickness of the screw mount affect the performance of the K mount lenses? Especially as involves vignetting, let alone infinity focus? there is no noticeable change in the vignetting, because whatever thicknesses we are talking about here by adding the adapter are tiny to non-existent... remember that a real pentax factory m42 to pk adapter hits infinity focus just about every time on a pentax camera, while the aftermarket m42 to pk adapters don't. since all cheap nex adapters are deliberately sized to let the lens focus beyond infinity, adding even an aftermarket m42 to pk adapter to the nex adapter still leaves plenty of room for infinity focus... i know because i've done it. the key to working with nex adapters is to remember that hard infinity focus stops on lenses are an obsolete dslr concept, that doesn't apply here... evf magnification is more accurate than any autofocus system will ever be, if you have time to use it, and even then you still have focus peaking to work with.

02-04-2015, 12:46 PM	#5
BAB Forum Member Join Date: Jul 2008 Location: Maine, USA Posts: 66 Original Poster	Originally posted by vonBaloney So you're saying your m42 adapter is stuck in the PK/E adapter, but you can still mount K lenses? Sounds potentially dangerous (to the K lenses)... The adapter is designed that way.......it's only the central screw mount portion that is removable, leaving a K-mount adapter that mounts K-mount lenses. It's the extra thickness of the adapter upon which K-mount lenses are mounted that is my chief question. I.e., does not the extra thickness change the performance of the K-mount lens? BAB

02-04-2015, 12:50 PM	#6
BAB Forum Member Join Date: Jul 2008 Location: Maine, USA Posts: 66 Original Poster	Originally posted by wtlwdwgn The answer to the last question is no. An M42 adapter should be mounted to the camera first and then the lens screwed into the adapter. The lens will begin to unscrew if you attempt to remove both. The Pentax M42 adapter has a spring clip which holds the adapter in place. I just use a finger nail to release the spring to remove the adapter. I wouldn't try to use any kind of 'tool' as you might break the spring and it will become permanently stuck. Yes, I'm aware of that. But why is there not provision for removing the adapter ring, which was my primary question.......does the extra thickness of the adapter ring change the performance of the K lens mounted on top of it? Thanks, BAB

02-04-2015, 12:51 PM	#7
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	Originally posted by BAB does the extra thickness of the adapter ring change the performance of the K lens mounted on top of it? for the second time... NO

02-04-2015, 12:55 PM	#8
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by BAB The adapter is designed that way...... Which adapter is designed that way? The Sony/PK adapter? Because any PK/M42 adapter is not designed to have K mount lenses "mounted on top of it" -- makes no sense.

02-04-2015, 12:56 PM	#9
BAB Forum Member Join Date: Jul 2008 Location: Maine, USA Posts: 66 Original Poster	Originally posted by dcshooter Sounds like it might have got pushed off the bayonet and fallen into the Sony adapter. If you remove the screws from the front of the Sony adapter, you shold be able to lift the bayonet out and retrieve your m42 adapter. No, I don't think that possible. The screwmount portion of the adapter ring is removable ...... an is actually here on my desk top. ---------- Post added 02-04-15 at 12:49 PM ---------- Also, does your m42 to Pentax K adapter look like this: Type 1 (e.g. the genuine Pentax branded adapter) does not introduce extra thickness, while type #2 does. That one will cause you to lose infinity focus. The adapter I bought is the original Pentax branded adapter. It's good to know I won't lose infinity focus (difficult to ascertain unless I go outside, and it's 10 degrees and I don't want to go outside . BUT WHAT ABOUT VIGNETTING? Thanks for the reply........ BAB

02-04-2015, 01:02 PM	#10
BAB Forum Member Join Date: Jul 2008 Location: Maine, USA Posts: 66 Original Poster	Originally posted by vonBaloney Which adapter is designed that way? The Sony/PK adapter? Because any PK/M42 adapter is not designed to have K mount lenses "mounted on top of it" -- makes no sense. Um, yes it does, as with the original Pentax adapter (which I didn't know until I mounted the adapter) has a central ring which is removable when clicking a retaining ring. The central ring is an M42 threaded ring. With that ring removed, the adapter is a plain old PK mount ring and one can mount PK lenses to it. My question is, how does the extra thickness of the adapter ring affect the performance of the lens. One respondent has indicated it won't affect infinity focus of K-mount lenses, but what about VIGNETTING? You might be confused, in that I've mounted the Pentax Takumar adapter to Pentax K to Sony E adapter already on the camera. Sorry for the confusion. BAB ---------- Post added 02-04-2015 at 03:04 PM ---------- Originally posted by dcshooter The m42 lenses are designed to provide full coverage of a 35mm film frame when mounted at the appropriate distance from the film plane. This is the same distance the adapter holds it from your sensor, so it shouldn't vignette, even on a full-frame sensor like the A7. Thanks, but what I meant was vignetting of K lenses, because of the extra thickness now present due to the adapter. BAB

02-04-2015, 01:35 PM	#11
BAB Forum Member Join Date: Jul 2008 Location: Maine, USA Posts: 66 Original Poster	HOLD THE PRESSES !!! The Pentax Takumar adapter fits inside the K-mount. Duh. I have no idea where I got the idea that there was a second ring that mounted on top of the original K-mount. I am NOT going crazy. I just need my eyes examined. Thanks much for sending me back to the mount to examine the mount with non-paranoid eyes BAB

02-04-2015, 01:59 PM	#12
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by BAB HOLD THE PRESSES !!! The Pentax Takumar adapter fits inside the K-mount. Duh. I have no idea where I got the idea that there was a second ring that mounted on top of the original K-mount. I am NOT going crazy. I just need my eyes examined. Yes, that's right. The adapter IS the ring (and that's all it is), and the adapter itself IS a K-mount. That's why it makes no sense to say you could then mount K-mount lenses on top of it with it installed because its whole purpose is to take a K-mount and turn it into a (narrower) m42 screw mount. There are ones with an extra flange that sticks outside the mount (messing up infinity focus) -- see the pics posted above of the two versions...

02-04-2015, 02:47 PM	#13
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	The instruction manual for the genuine Pentax K mount adapter: http://www.gyes.eu/documents/pentax_mount_adapter_k.pdf Most of the time you can use your thumbnail instead of a ball-point pen. Or you can look in most of the manual focus Pentax camera manuals.

02-04-2015, 02:47 PM	#14
dms Site Supporter Join Date: Aug 2011 Location: New York, NY Photos: Gallery Posts: 2,192	If you remove the spring clip the adapter will stay on the lens when you remove it--but it requires a small cross screwdriver to do this--and if not careful the screw head will be stripped--so it cannot be removed.