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03-01-2010, 12:17 PM   #1
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K20D & Old Film K-Mount Lenses

I just got a hold of a NOS Pentax K20D. The lens I had available to test with is a Sigma 28-70mm KA mount lens (so it has the "A" lock). I wanted to use the K20D's'"all manual" mode so that I could adjust the F-stop with the lens ring instead of the camera. However every mode I select, the LCD display flashes "F---" and doesn't let me do anything until I lock the F-stop ring into the "A" setting and let the camera take control of the f-stops.

Is this happening because the camera senses that it is a KA lens and not a manual K lens? The main reason why I got this camera was so that I could use my old film lenses. If it can't do that, then my old lenses are useless!

Am I doing something wrong in the settings, or do I have to use an actual "K" all-manual film lens for the K20D to go into full manual mode?

03-01-2010, 12:54 PM   #2
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QuoteOriginally posted by MGarcia Quote
I just got a hold of a NOS Pentax K20D. The lens I had available to test with is a Sigma 28-70mm KA mount lens (so it has the "A" lock). I wanted to use the K20D's'"all manual" mode so that I could adjust the F-stop with the lens ring instead of the camera. However every mode I select, the LCD display flashes "F---" and doesn't let me do anything until I lock the F-stop ring into the "A" setting and let the camera take control of the f-stops.

Is this happening because the camera senses that it is a KA lens and not a manual K lens? The main reason why I got this camera was so that I could use my old film lenses. If it can't do that, then my old lenses are useless!

Am I doing something wrong in the settings, or do I have to use an actual "K" all-manual film lens for the K20D to go into full manual mode?
Go in to the custom menu and select the option that says "Using Aperture Ring" and turn it on. Then enjoy the camera.

03-01-2010, 01:08 PM   #3
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To expand a bit on Jeff's correct answer: The A lenses will work exactly as older K and M lenses, if you use any other position of the aperture ring, than the A-setting. This is, because outside the A-setting, the tiny A-contact in the lens mount will be withdrawn and won't make contact with the camera's counterpart. If the A-setting is engaged, the lens contact will protract and get into contact with the camera's contact and only then the camera knows about the A-lens.

Any manual aperture lens will only work correctly, if you set the Use Aperture Ring Allowed in the custom menue. It is all in the very good K20 manual!

Ben
03-01-2010, 01:45 PM   #4
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Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you!!!!!!!!!!!!!

I knew it had to be something simple!!

03-02-2010, 03:18 PM   #5
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To expand further: see the sticky thread at the top of this very forum on using manual lenses for very detailed instructions.
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