Modify a 50mm 1:1,2

Balticthor · 11-17-2009, 05:05 PM

I have both a Pentax M 50mm 1:1,2 and a A 50mm 1:1,7
And i want to use the 1:1,2 with most ease on my K-m.. Is it possible to rebuild the lenses so i get the 1:1,2 with automatic and the 1:1,7 without? with the parts that i have within the two lenses?
I dont have the lenses with me now so i cant inspect them,sorry is it is a stupid question..hehe

SOldBear · 11-17-2009, 05:11 PM

Don't do it.

It's not a simple case of drilling a few holes in the lens mount to add electrical contacts. The aperture actions of the two lenses are different.

Modifying M-lenses into A-lenses have been topics of many threads. No one has reported a successful case yet.

RawheaD · 11-17-2009, 05:11 PM

Not so much what you need to do with the lenses, but rather what you need to do to your cam:

vietlh81: How to convert the K-M lens to KA lens

Andi Lo · 11-17-2009, 05:15 PM

Originally posted by RawheaD

Not so much what you need to do with the lenses, but rather what you need to do to your cam:

vietlh81: How to convert the K-M lens to KA lens

Does anyone know if there's any adverse effect on doing this when using a normal A lens? Would be interesting if I can use this method on my M40/2.8

troyz · 11-17-2009, 05:20 PM

Originally posted by Andi Lo

Does anyone know if there's any adverse effect on doing this when using a normal A lens? Would be interesting if I can use this method on my M40/2.8

The adverse effect is that it doesn't work.

Sure, you can trick the camera into thinking that the K lens is a KA -- you still don't get accurate control of aperture from the body.

**Lowell Goudge** · 11-17-2009, 06:22 PM

the bottom line is that you will be ruining a lens worht hundreds of dollars to create a lens that does not perform worth a s#!% in A mode.

I converted a 50mmF2 (XR Rikinon) to an A lens by adding an A contact and coding the apertures to match the correct KA lens contact pattern.

did it function, yes, but metering went from -1 stop under exposed to +2 stops over exposed due to the above mentioned differences in aperture control.

It just is not worth it.

If you go out and get an SMC-A 50mmF1.4 it will cost less than the devaluation of the SMC-50mm F1.2

Marc Sabatella · 11-17-2009, 06:55 PM

Originally posted by Balticthor

I have both a Pentax M 50mm 1:1,2 and a A 50mm 1:1,7
And i want to use the 1:1,2 with most ease on my K-m.. Is it possible to rebuild the lenses so i get the 1:1,2 with automatic and the 1:1,7 without? with the parts that i have within the two lenses?
I dont have the lenses with me now so i cant inspect them,sorry is it is a stupid question..hehe

BTW, there is no "M" version of the 50/1.2, although there was a "K" (officially, just called "SMC Pentax"). So I assume that's the one you have, and not in fact an "M" lens? Not that I think that you are making this mistake, but many people confuse 1:2 with 1.2...

little laker · 11-17-2009, 11:46 PM

Originally posted by RawheaD

Not so much what you need to do with the lenses, but rather what you need to do to your cam:

vietlh81: How to convert the K-M lens to KA lens

I don't know how current that site is, however it's saying that doesn't work on digital

frank · 11-18-2009, 12:55 AM

As the others said above, it's not as simple as just adding an A contact.

I tried that on my K50/1.2 lens: drilled a hole at the right location, put an A contact there. The camera recongnized the lens as an A lens, but when I used the rear wheel (on my K7 camera) to adjust/control the aperture, the metering wasn't as expected from an A lens. It did stop down the lens though, but the aperture I set on the camera wasn't really the one I got from the results. Sometimes the metering could be way off.

After that trial, I gave up on the idea and just keep using the lens as a full manual one instead.

GerryL · 11-20-2009, 03:46 PM

Hmm..so a couple of people already tried this.
..and all the while I thought that nobody has and wanted to have a go at it myself!

11-17-2009, 05:05 PM	#1
Balticthor New Member Join Date: Nov 2009 Location: Aalesund Posts: 4	Modify a 50mm 1:1,2 I have both a Pentax M 50mm 1:1,2 and a A 50mm 1:1,7 And i want to use the 1:1,2 with most ease on my K-m.. Is it possible to rebuild the lenses so i get the 1:1,2 with automatic and the 1:1,7 without? with the parts that i have within the two lenses? I dont have the lenses with me now so i cant inspect them,sorry is it is a stupid question..hehe

11-18-2009, 12:55 AM	#9
frank Veteran Member Join Date: Nov 2006 Location: Singapore Photos: Gallery Posts: 3,202	As the others said above, it's not as simple as just adding an A contact. I tried that on my K50/1.2 lens: drilled a hole at the right location, put an A contact there. The camera recongnized the lens as an A lens, but when I used the rear wheel (on my K7 camera) to adjust/control the aperture, the metering wasn't as expected from an A lens. It did stop down the lens though, but the aperture I set on the camera wasn't really the one I got from the results. Sometimes the metering could be way off. After that trial, I gave up on the idea and just keep using the lens as a full manual one instead. Last edited by frank; 11-22-2009 at 09:39 PM.

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11-17-2009, 05:11 PM	#2
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Don't do it. It's not a simple case of drilling a few holes in the lens mount to add electrical contacts. The aperture actions of the two lenses are different. Modifying M-lenses into A-lenses have been topics of many threads. No one has reported a successful case yet.

11-17-2009, 05:11 PM	#3
RawheaD Veteran Member Join Date: Dec 2008 Location: MA, USA Photos: Gallery Posts: 831	Not so much what you need to do with the lenses, but rather what you need to do to your cam: vietlh81: How to convert the K-M lens to KA lens

11-17-2009, 05:15 PM	#4
Andi Lo Veteran Member Join Date: Jul 2008 Location: Halifax, Nova Scotia Posts: 2,924	Originally posted by RawheaD Not so much what you need to do with the lenses, but rather what you need to do to your cam: vietlh81: How to convert the K-M lens to KA lens Does anyone know if there's any adverse effect on doing this when using a normal A lens? Would be interesting if I can use this method on my M40/2.8

11-17-2009, 05:20 PM	#5
troyz Veteran Member Join Date: May 2008 Posts: 389	Originally posted by Andi Lo Does anyone know if there's any adverse effect on doing this when using a normal A lens? Would be interesting if I can use this method on my M40/2.8 The adverse effect is that it doesn't work. Sure, you can trick the camera into thinking that the K lens is a KA -- you still don't get accurate control of aperture from the body.

11-17-2009, 06:22 PM	#6
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,888	the bottom line is that you will be ruining a lens worht hundreds of dollars to create a lens that does not perform worth a s#!% in A mode. I converted a 50mmF2 (XR Rikinon) to an A lens by adding an A contact and coding the apertures to match the correct KA lens contact pattern. did it function, yes, but metering went from -1 stop under exposed to +2 stops over exposed due to the above mentioned differences in aperture control. It just is not worth it. If you go out and get an SMC-A 50mmF1.4 it will cost less than the devaluation of the SMC-50mm F1.2

11-17-2009, 06:55 PM	#7
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by Balticthor I have both a Pentax M 50mm 1:1,2 and a A 50mm 1:1,7 And i want to use the 1:1,2 with most ease on my K-m.. Is it possible to rebuild the lenses so i get the 1:1,2 with automatic and the 1:1,7 without? with the parts that i have within the two lenses? I dont have the lenses with me now so i cant inspect them,sorry is it is a stupid question..hehe BTW, there is no "M" version of the 50/1.2, although there was a "K" (officially, just called "SMC Pentax"). So I assume that's the one you have, and not in fact an "M" lens? Not that I think that you are making this mistake, but many people confuse 1:2 with 1.2...

11-17-2009, 11:46 PM	#8
little laker Veteran Member Join Date: Sep 2006 Photos: Gallery Posts: 5,697	Originally posted by RawheaD Not so much what you need to do with the lenses, but rather what you need to do to your cam: vietlh81: How to convert the K-M lens to KA lens I don't know how current that site is, however it's saying that doesn't work on digital

11-20-2009, 03:46 PM	#10
GerryL Veteran Member Join Date: Jan 2009 Location: CA Posts: 2,731	Hmm..so a couple of people already tried this. ..and all the while I thought that nobody has and wanted to have a go at it myself!