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03-19-2010, 04:03 PM   #1
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Using prime lens with Kx?

I just received my first prime lens in the mail and went to test it out...and it doesn't shoot. Tried several different settings, modes, etc... and couldn't get it to work. Is there something that I don't know? Obviously i need to set the aperture and focus it manually(being an M series lens), but I can't get it to work at all! Please advise.

03-19-2010, 04:06 PM   #2
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Totally forgot to mention that the body is a Kx and the lens a 1.7 50mm SMC-M
03-19-2010, 04:33 PM   #3
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Don't own a K-x but if it's anything like the K7, there is a menu option to enable the use of the aperture ring on the lens. You'll need to check your manual, i'm not sure how to get to this setting. Hope this helps, roliver.
03-19-2010, 04:45 PM   #4
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See the first (sticky) post atop the Beginner's Forum: https://www.pentaxforums.com/forums/pentax-beginners-corner-q/59272-shooting-...x-dslrs-f.html

03-19-2010, 04:55 PM   #5
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QuoteOriginally posted by roliver Quote
Don't own a K-x but if it's anything like the K7, there is a menu option to enable the use of the aperture ring on the lens. You'll need to check your manual, i'm not sure how to get to this setting. Hope this helps, roliver.
Thanks, I had looked in the manual underneath "manual lenses" and a few other things, but never for aperture ring.

QuoteOriginally posted by RioRico Quote
Thanks, I feel stupid now. I had actually read partway through this post, and thought things seemed so different on my camera. I stopped reading and posted here, my fault. Thanks to both of you.
03-20-2010, 10:32 AM   #6
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Set your green button for TV shift, and shoot in M mode.

You select your aperture and focus, or focus wide open and then set your aperture, and hit the green button, which will lock in the correct shutter speed. You are essentially shooting in Av mode, but you can't CHOOSE Av mode on the camera, because that always shoots wide open. (The camera can't communicate with the lens's set aperture and doesn't know what to do.)

Guys, am I right? I know this is how it is with Taks, so is it the same for M?
03-20-2010, 10:38 AM   #7
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For the m series lenses you can not use av mode since the aperature can not be controlled via av mode and there is not manual mode for aperture like those in the takumar or m42 lenses.
03-20-2010, 11:25 AM   #8
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QuoteOriginally posted by epqwerty Quote
For the m series lenses you can not use av mode since the aperature can not be controlled via av mode and there is not manual mode for aperture like those in the takumar or m42 lenses.
Actually, you can use Av, but the aperture will always be wide open. The screw mount lenses become manual aperture lenses when you set the control to M or Manual from A or Automatic. In Av mode with the lens set to A, they expose only wide open.

For those not in the know (and you have to be as old as I am to be in the know without a history book), Aperture control falls into three general categories:
  1. Manual. The aperture follows the ring as you turn it. This was quite common back when.
  2. Preset. There are two rings, one of which you set to the exposure and the other of which turns freely between that and wide open, allowing focus wide open and exposure stopped down without looking. This is one of my favourite systems. My first Pentax had no mechanism to stop down the lens, so these were the lenses I used with it.
  3. Automatic. The aperture stops down when the shutter is released. Most lenses from Asahi/Pentax fall into this category. On the DSLR models, one of the traces is missing from the mount (crippled mount) and lenses not set to the A setting on the aperture ring will not be controlled by the camera body, except in M exposure mode.


03-21-2010, 10:49 AM   #9
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QuoteOriginally posted by Canada_Rockies Quote
Actually, you can use Av, but the aperture will always be wide open. The screw mount lenses become manual aperture lenses when you set the control to M or Manual from A or Automatic. In Av mode with the lens set to A, they expose only wide open.

For those not in the know (and you have to be as old as I am to be in the know without a history book), Aperture control falls into three general categories:
  1. Manual. The aperture follows the ring as you turn it. This was quite common back when.
  2. Preset. There are two rings, one of which you set to the exposure and the other of which turns freely between that and wide open, allowing focus wide open and exposure stopped down without looking. This is one of my favourite systems. My first Pentax had no mechanism to stop down the lens, so these were the lenses I used with it.
  3. Automatic. The aperture stops down when the shutter is released. Most lenses from Asahi/Pentax fall into this category. On the DSLR models, one of the traces is missing from the mount (crippled mount) and lenses not set to the A setting on the aperture ring will not be controlled by the camera body, except in M exposure mode.
I've been looking this morning at the possibility of modifying some of these old lenses to trick the camera into believing that you have in fact mounted an 'A'-type lens. Found this: modified pentax-m 50mm f1.4 on Flickr - Photo Sharing! . The guy is using steel wool to make an electrical contact with the recessed 'A' pin in the body when the lens is attached. He has also drilled some small divots into the lens to break contact with the pins on the mount although I understand that this can be done with non-conducting tape. Apparently, using this method, one can adjust the aperture of the lens from the camera although I've read that some people have had problems with over/under exposure. Whatever the case, it may be worth looking at because it can be done without any permanent changes to the body/lens. A table of aperture range pin combinations can be found here: http://www.robertstech.com/matrix.htm

Last edited by roliver; 03-21-2010 at 10:54 AM. Reason: forgotton link
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