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09-02-2011, 06:46 PM   #1
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Pentax-M lens -- trouble stopping down

I was testing my new Pentax-M 50mm f1.7 lens today. It's my first manual lens (have it mounted on my K-x), so I was testing out different apertures to get a feel for corresponding shutters speeds in various light conditions.

When I focused on a bright, sunlit area on the side of my house (has pretty light colored, yellow shingles), set the aperture to wide-open (f1.7) then pressed the green button to stop down, the shutter speed went up to .3 of a sec. It was the same for the next couple F-stops, until finally, around 4 or so, the shutter speed went back up to 1/400 or something thereabouts.

Has anyone had this experience before? Was there just too much light getting to the sensor with lens wide-open that everything went wacko? I really don't understand it.


09-02-2011, 06:50 PM   #2
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Yes, there was too much light. When the shutter speed required to get the correct exposure is greater than 1/6000 in the k-x, it automatically shows 0.3.
09-02-2011, 07:59 PM   #3
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Not wacko, this is intended behavior. The amount of light is more than the camera can handle at it's fastest speed so it shows .3. I personally think it should show something else like 'OL' or an up arrow or anything except an answer that can be confused as both an expected exposure and an out of bounds reading.

But as Jindesu says it is just too much light. Adjust ISO or aperture until you get within the capabilities of the camera.

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