Alignment of rectangular window on Takumar M42 lenses

abhaskare · 02-07-2017, 05:22 PM

Some of the Takumar lenses have a rectangular window at the rear,
Is there any trick to get this aligned with the screw to K adapter? I found a thread on this topic but that does not discuss how to align this.
I would be using it on my K5II

Attached Images

**Lowell Goudge** · 02-07-2017, 07:14 PM

Given the takumars were designed for full frame, this window will not interfere at all with a crop sensor camera like the K5

Even on a k1 it is unlikely to be an issue because it will have margin for a full frame body, what it does is actually limit stay light from the mirror box

**Lowell Goudge** · 02-07-2017, 08:49 PM

Originally posted by Lowell Goudge

Given the takumars were designed for full frame, this window will not interfere at all with a crop sensor camera like the K5

Even on a k1 it is unlikely to be an issue because it will have margin for a full frame body, what it does is actually limit stay light from the mirror box

As an afterthought, remember crop sensor is 16x 24 mm, full frame is 24x36mm

You could mount this 90degrees off and not have an issue

**beachgardener** · 02-07-2017, 11:52 PM

Originally posted by dcshooter

The OEM Pentax adapter is designed so lenses will sit slightly off 12 o'clock when fully tightened

yes I have noticed this with my M42 lenses with the Pentax adapter, why is that do you think?

Not a Number · 02-08-2017, 07:09 AM

A few people report that their lenses will mount aligned to the 12 o'clock position. I have 3 OEM adapters - one branded Pentax Japan and the other two branded Pentax Philippines. None align to 12 o'clock. I wonder if the Asahi Pentax Japan branded adapters are different or perhaps only a run up to a certain point.

abhaskare · 02-08-2017, 07:59 AM

Thank you all for the nice responses that answered my doubts!
I think I can safely look at buying one of those lenses and if I wanted, I can clear that opening (which I doubt would do if nothing is interefering!)
Appreciate the feedback from all -

**beachgardener** · 02-08-2017, 08:07 PM

thanks for your answer, makes sense, cheers.

Not a Number · 02-09-2017, 06:43 AM

Originally posted by dcshooter

My theory might be wrong. I just double checked with two MIJ adapters, one marked "Asahi Pentax," and one just "PENTAX," and both mount with the lens at about The 11 o'clock position. For more clearance for the switch, one would assume it would be offset the other way, at 1 o'clock. The plot thickens..

On my Vivitar screw mount lenses the A/M switch is located 180° from where it is on Takumars. I find it very inconveniently located and difficult to operate. The lower profile of the switch doesn't help either. I would suppose that back in the day users with bodies lacking the auto aperture feature were just used to manually stopping down or using pre-set lenses that they would just leave it on manual.

Another theory is that the offset is to make it easier to read the scales on the lens because of the prism overhang.

Or it could be the built-in tolerance to allow for individual variation of lenses.

02-07-2017, 05:22 PM	#1
abhaskare Senior Member Join Date: Jan 2016 Location: Phoenixville, PA Posts: 136	Alignment of rectangular window on Takumar M42 lenses Some of the Takumar lenses have a rectangular window at the rear, Is there any trick to get this aligned with the screw to K adapter? I found a thread on this topic but that does not discuss how to align this. I would be using it on my K5II Attached Images

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02-07-2017, 07:14 PM	#2
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,891	Given the takumars were designed for full frame, this window will not interfere at all with a crop sensor camera like the K5 Even on a k1 it is unlikely to be an issue because it will have margin for a full frame body, what it does is actually limit stay light from the mirror box

02-07-2017, 08:49 PM	#3
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,891	Originally posted by Lowell Goudge Given the takumars were designed for full frame, this window will not interfere at all with a crop sensor camera like the K5 Even on a k1 it is unlikely to be an issue because it will have margin for a full frame body, what it does is actually limit stay light from the mirror box As an afterthought, remember crop sensor is 16x 24 mm, full frame is 24x36mm You could mount this 90degrees off and not have an issue

02-07-2017, 11:52 PM	#4
beachgardener Site Supporter Join Date: Sep 2013 Location: Australia Photos: Gallery Posts: 3,842	Originally posted by dcshooter The OEM Pentax adapter is designed so lenses will sit slightly off 12 o'clock when fully tightened yes I have noticed this with my M42 lenses with the Pentax adapter, why is that do you think?

02-08-2017, 07:09 AM	#5
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	A few people report that their lenses will mount aligned to the 12 o'clock position. I have 3 OEM adapters - one branded Pentax Japan and the other two branded Pentax Philippines. None align to 12 o'clock. I wonder if the Asahi Pentax Japan branded adapters are different or perhaps only a run up to a certain point.

02-08-2017, 07:59 AM	#6
abhaskare Senior Member Join Date: Jan 2016 Location: Phoenixville, PA Posts: 136 Original Poster	Thank you all for the nice responses that answered my doubts! I think I can safely look at buying one of those lenses and if I wanted, I can clear that opening (which I doubt would do if nothing is interefering!) Appreciate the feedback from all -

02-08-2017, 08:07 PM	#7
beachgardener Site Supporter Join Date: Sep 2013 Location: Australia Photos: Gallery Posts: 3,842	thanks for your answer, makes sense, cheers.

02-09-2017, 06:43 AM	#8
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Originally posted by dcshooter My theory might be wrong. I just double checked with two MIJ adapters, one marked "Asahi Pentax," and one just "PENTAX," and both mount with the lens at about The 11 o'clock position. For more clearance for the switch, one would assume it would be offset the other way, at 1 o'clock. The plot thickens.. On my Vivitar screw mount lenses the A/M switch is located 180° from where it is on Takumars. I find it very inconveniently located and difficult to operate. The lower profile of the switch doesn't help either. I would suppose that back in the day users with bodies lacking the auto aperture feature were just used to manually stopping down or using pre-set lenses that they would just leave it on manual. Another theory is that the offset is to make it easier to read the scales on the lens because of the prism overhang. Or it could be the built-in tolerance to allow for individual variation of lenses.