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Forum: Pentax DSLR Discussion
11-19-2010, 08:39 AM
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To clear up what may be a little confusion, here are the tubes in question, your basic set of PK mount auto extension tubes. They are black aluminum, though I guess that's just the anodized coating.
On my K20, in Manual mode, I get stop down metering when pushing the green button (Use Aperture Ring - set to on), i.e. camera will set an appropriate shutter speed based on stopping down the aperture to what the ring on the lens is set to.
On Mike's K-x, when he tries to perform the same function, the aperture doesn't stop down with tubes attached between the mount and lens. If only the manual lens is mounted to the camera, it stops down normally for the meter reading.
On my K20, manual mode, no lens attached, the aperture lever will actuate when the green button is depressed whether or not I short any of the pins, i.e. the camera body doesn't care that nothing's attached, it will try to meter by actuating the aperture lever on the body
On Mike's K-x, this apparently does not happen except when he shorts a pin. So, it sounds to me like it's a firmware issue with the K-x, i.e. it will only actuate the aperture lever if there's conductive metal attached to the mount. I verified that the black coating is non-conductive with my DMM set to a continuity test mode.
I also checked some spots where there was some brassing or bare aluminum exposed and the continuity checked good. So, I suppose I could scratch the anodized coating so his K-x would recognize them, or I could just let him hang and get his own set. Hmmm.... ;)
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Forum: Pentax DSLR Discussion
11-18-2010, 03:44 PM
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I'll just throw this in to keep the can o' worms open a bit longer. Don't the K20D and K-x (or any modern Pentax for that matter) all have the same KA2 crippled mount? If so, seems like the only reason I could think of would be firmware.
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