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.
Thanks,
Brian
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