SMC Pentax-A 50mm F1.7 Problem

bluemarvin · 11-07-2012, 08:01 AM

First post - so apologies if in wrong forum. Currently using a Samsung

GX20 with a Pentax DA 16-45 - all working well (and in my defence the GX20 was preceded by an SF7 and an ME Super). Then I got this Pentax-A 50mm F1.7 - but when on the GX20, its aperture is shown as F-.-. and I can't take any pics regardless of camera settings (and I have used menu to select 'Aperture Ring' - but made no difference). The mechanics of the lens appear to work fine but I'm suspecting it has been fiddled with - should there be an open hole in the contact group area of the mount? - between 2 and 3 o'clock in the attached picture.

Any advice on cause of problem or ways to fix very welcome.

Attached Images

View Picture EXIF

Boker · 11-07-2012, 08:08 AM

You have a contact pin missing.You should be able to use the lens as a M type

bluemarvin · 11-07-2012, 08:28 AM

Thanks very much - you are quite right - it will take pictures with the camera set on aperture priority. Is there likely to be any sensible way of repairing it?

Boker · 11-07-2012, 08:32 AM

Think it will stay wide open in Av mode but will work properly in M

**Just1MoreDave** · 11-07-2012, 08:44 AM - **1 Like**

This article shows what's missing: https://www.pentaxforums.com/forums/maintenance-repair-articles/88051-pentax-...ng-repair.html

I've read about using different things to replace the contact. It needs to be spring-loaded or the lens won't mount. That's the tricky part.

bluemarvin · 11-07-2012, 09:06 AM

Again you are right about Av mode - the camera always takes the picture at f1.7 - but in M mode I get no indication of aperture so no indication of over/under exposure - so not a lot of use! Unless the lens can be fixed I'll dump it & get one that works.

thanks again

bluemarvin · 11-07-2012, 09:09 AM

@ Just1MoreDave - thanks very much - article spot-on

**JimJohnson** · 11-07-2012, 01:58 PM

Originally posted by bluemarvin

Any advice on cause of problem or ways to fix very welcome.

Ideally you will repair the lens. The missing contact is the pin that extends itself when the aperture ring is locked in the 'A' position. There IS a fix you can apply in only a few minutes time that will restore full functionality to this lens.
https://www.pentaxforums.com/forums/pentax-k-r/178928-kr-short-contacts-chang...ml#post1867401

Once you short the contact as described, simply lock the aperture ring in the 'A' position and you will have full functionality with the camera and lens until (if) you decide to repair it.

bluemarvin · 11-07-2012, 02:52 PM

Originally posted by JimJohnson

Ideally you will repair the lens. The missing contact is the pin that extends itself when the aperture ring is locked in the 'A' position. There IS a fix you can apply in only a few minutes time that will restore full functionality to this lens.
https://www.pentaxforums.com/forums/pentax-k-r/178928-kr-short-contacts-chang...ml#post1867401

Once you short the contact as described, simply lock the aperture ring in the 'A' position and you will have full functionality with the camera and lens until (if) you decide to repair it.

Thanks for that - I'm a little bit wary of modifying the camera as it works fine with my other lenses. I'll try to fix this lens if I can find the bits.

hks_kansei · 11-07-2012, 04:16 PM

If you need parts you may be able to buy the relatively cheap A series F2 lens.

I'm not cure if the parts are interchangable, but I imagine they would be.

**JimJohnson** · 11-07-2012, 04:37 PM

Originally posted by bluemarvin

Thanks for that - I'm a little bit wary of modifying the camera as it works fine with my other lenses.

Obviously it is your choice. That said, shorting out the A pin on the body is easily, quickly and 100% reversible if you don't like it; further it will work just fine with any lens you can mount on your camera. The only difference is your camera will think all your lens are 'A' capable ... if a lens is 'A' capable, absolutely NO difference in performance. If the lens is a non-A, manual lens you use it exactly the same as you always did, only now you will see an aperture value and won't see "F - - -".

I have two Pentax A-series lenses, one F-series, three DA-series, a Sigma F-series equivalent lens. I frequently mount my A-50mm f/1.7 on a manual macro-converter giving me the equivalent of an M-series lens, and I have a Pentax K-mount bellows unit. Everything works perfectly, and I've never found a need to undo this modification. In another post in this forum I proved that I could even successfully do P-TTL flash photography using a borrowed M-50mm f/1.2 lens.

bluemarvin · 11-08-2012, 01:22 AM

Thanks to everyone for help/advice. Not at home for next 2 weeks so can't try repairs/mods - but will report on progress when I get back.

cheers

Marc Sabatella · 11-08-2012, 08:24 PM

Originally posted by bluemarvin

Again you are right about Av mode - the camera always takes the picture at f1.7 - but in M mode I get no indication of aperture so no indication of over/under exposure - so not a lot of use!

Not sure if you've already figured this out or not, but the above is *not* true. I mean, yes, it's true that you don't get an indication of aperture, but that doesn't meant you can't get an indication of over/underexposure. You just need to get the camera to stop down the lens for you, by doing DOF preview. Or simply hit the Green button so the camera will automatically stop the lens down, take a meter reading, and set an appropriate shutter speed for you. Do a search and you should be able to find any number of articles explaining more about how to use manual lenses. Some of us use them a lot! With the Green button and DOF preview, it's really not much less convenient than using an "A" lens.

jamesm007 · 11-08-2012, 09:33 PM

The contact pin is in the wrong hole. I can tell by looking at the screws and lens retainer someone took this lens apart before and when they put it back together things gut ugly. Take a look at all Pentax A only primes as yours. What you are missing is the little white cap that goes where the contact is now. You can try to move the contact over by removing the back cover very carefully. Have a magnet pickup tool ready. A small steel ball will come out and perhaps a spring or two. Thats what happened last time. But just remove the cover slow and aperture ring slow. The steel ball you don't see that I am talking about provided the clicks as you move the aperture ring.

I see others give you links to repair. But just know its in the wrong hole!

Boker · 11-08-2012, 09:53 PM

Originally posted by jamesm007

The contact pin is in the wrong hole. I can tell by looking at the screws and lens retainer someone took this lens apart before and when they put it back together things gut ugly. Take a look at all Pentax A only primes as yours. What you are missing is the little white cap that goes where the contact is now. You can try to move the contact over by removing the back cover very carefully. Have a magnet pickup tool ready. A small steel ball will come out and perhaps a spring or two. Thats what happened last time. But just remove the cover slow and aperture ring slow. The steel ball you don't see that I am talking about provided the clicks as you move the aperture ring.

I see others give you links to repair. But just know its in the wrong hole!

Good catch,you are absolutely right

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11-07-2012, 08:08 AM	#2
Boker Senior Member Join Date: Jul 2012 Location: SW Florida Posts: 234	You have a contact pin missing.You should be able to use the lens as a M type

11-07-2012, 08:28 AM	#3
bluemarvin New Member Join Date: Nov 2012 Posts: 10 Original Poster	Thanks very much - you are quite right - it will take pictures with the camera set on aperture priority. Is there likely to be any sensible way of repairing it?

11-07-2012, 08:32 AM	#4
Boker Senior Member Join Date: Jul 2012 Location: SW Florida Posts: 234	Think it will stay wide open in Av mode but will work properly in M

11-07-2012, 08:44 AM - 1 Like	#5
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	This article shows what's missing: https://www.pentaxforums.com/forums/maintenance-repair-articles/88051-pentax-...ng-repair.html I've read about using different things to replace the contact. It needs to be spring-loaded or the lens won't mount. That's the tricky part.

11-07-2012, 09:06 AM	#6
bluemarvin New Member Join Date: Nov 2012 Posts: 10 Original Poster	Again you are right about Av mode - the camera always takes the picture at f1.7 - but in M mode I get no indication of aperture so no indication of over/under exposure - so not a lot of use! Unless the lens can be fixed I'll dump it & get one that works. thanks again

11-07-2012, 09:09 AM	#7
bluemarvin New Member Join Date: Nov 2012 Posts: 10 Original Poster	@ Just1MoreDave - thanks very much - article spot-on

11-07-2012, 01:58 PM	#8
JimJohnson Loyal Site Supporter Join Date: Jan 2012 Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country Photos: Gallery Posts: 2,772	Originally posted by bluemarvin Any advice on cause of problem or ways to fix very welcome. Ideally you will repair the lens. The missing contact is the pin that extends itself when the aperture ring is locked in the 'A' position. There IS a fix you can apply in only a few minutes time that will restore full functionality to this lens. https://www.pentaxforums.com/forums/pentax-k-r/178928-kr-short-contacts-chang...ml#post1867401 Once you short the contact as described, simply lock the aperture ring in the 'A' position and you will have full functionality with the camera and lens until (if) you decide to repair it.

11-07-2012, 02:52 PM	#9
bluemarvin New Member Join Date: Nov 2012 Posts: 10 Original Poster	Originally posted by JimJohnson Ideally you will repair the lens. The missing contact is the pin that extends itself when the aperture ring is locked in the 'A' position. There IS a fix you can apply in only a few minutes time that will restore full functionality to this lens. https://www.pentaxforums.com/forums/pentax-k-r/178928-kr-short-contacts-chang...ml#post1867401 Once you short the contact as described, simply lock the aperture ring in the 'A' position and you will have full functionality with the camera and lens until (if) you decide to repair it. Thanks for that - I'm a little bit wary of modifying the camera as it works fine with my other lenses. I'll try to fix this lens if I can find the bits.

11-07-2012, 04:16 PM	#10
hks_kansei Veteran Member Join Date: Jun 2012 Posts: 834	If you need parts you may be able to buy the relatively cheap A series F2 lens. I'm not cure if the parts are interchangable, but I imagine they would be.

11-07-2012, 04:37 PM	#11
JimJohnson Loyal Site Supporter Join Date: Jan 2012 Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country Photos: Gallery Posts: 2,772	Originally posted by bluemarvin Thanks for that - I'm a little bit wary of modifying the camera as it works fine with my other lenses. Obviously it is your choice. That said, shorting out the A pin on the body is easily, quickly and 100% reversible if you don't like it; further it will work just fine with any lens you can mount on your camera. The only difference is your camera will think all your lens are 'A' capable ... if a lens is 'A' capable, absolutely NO difference in performance. If the lens is a non-A, manual lens you use it exactly the same as you always did, only now you will see an aperture value and won't see "F - - -". I have two Pentax A-series lenses, one F-series, three DA-series, a Sigma F-series equivalent lens. I frequently mount my A-50mm f/1.7 on a manual macro-converter giving me the equivalent of an M-series lens, and I have a Pentax K-mount bellows unit. Everything works perfectly, and I've never found a need to undo this modification. In another post in this forum I proved that I could even successfully do P-TTL flash photography using a borrowed M-50mm f/1.2 lens.

11-08-2012, 01:22 AM	#12
bluemarvin New Member Join Date: Nov 2012 Posts: 10 Original Poster	Thanks to everyone for help/advice. Not at home for next 2 weeks so can't try repairs/mods - but will report on progress when I get back. cheers

11-08-2012, 08:24 PM	#13
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by bluemarvin Again you are right about Av mode - the camera always takes the picture at f1.7 - but in M mode I get no indication of aperture so no indication of over/under exposure - so not a lot of use! Not sure if you've already figured this out or not, but the above is not true. I mean, yes, it's true that you don't get an indication of aperture, but that doesn't meant you can't get an indication of over/underexposure. You just need to get the camera to stop down the lens for you, by doing DOF preview. Or simply hit the Green button so the camera will automatically stop the lens down, take a meter reading, and set an appropriate shutter speed for you. Do a search and you should be able to find any number of articles explaining more about how to use manual lenses. Some of us use them a lot! With the Green button and DOF preview, it's really not much less convenient than using an "A" lens.

11-08-2012, 09:33 PM	#14
jamesm007 Veteran Member Join Date: Jul 2008 Location: Detroit MI, USA Posts: 508	The contact pin is in the wrong hole. I can tell by looking at the screws and lens retainer someone took this lens apart before and when they put it back together things gut ugly. Take a look at all Pentax A only primes as yours. What you are missing is the little white cap that goes where the contact is now. You can try to move the contact over by removing the back cover very carefully. Have a magnet pickup tool ready. A small steel ball will come out and perhaps a spring or two. Thats what happened last time. But just remove the cover slow and aperture ring slow. The steel ball you don't see that I am talking about provided the clicks as you move the aperture ring. I see others give you links to repair. But just know its in the wrong hole!

11-08-2012, 09:53 PM	#15
Boker Senior Member Join Date: Jul 2012 Location: SW Florida Posts: 234	Originally posted by jamesm007 The contact pin is in the wrong hole. I can tell by looking at the screws and lens retainer someone took this lens apart before and when they put it back together things gut ugly. Take a look at all Pentax A only primes as yours. What you are missing is the little white cap that goes where the contact is now. You can try to move the contact over by removing the back cover very carefully. Have a magnet pickup tool ready. A small steel ball will come out and perhaps a spring or two. Thats what happened last time. But just remove the cover slow and aperture ring slow. The steel ball you don't see that I am talking about provided the clicks as you move the aperture ring. I see others give you links to repair. But just know its in the wrong hole! Good catch,you are absolutely right