Bill, I've found some exposure error as well with K and M series lenses and the green button. Somebody else mentioned it, and I don't understand it?
I thought the green button closed the aperture down and measured light exposure values. I can't imagine how this is off, but here is an example with K35/2 lens. (The lens was set at different apertures and green button pressed before exposure.) http://picasaweb.google.com/rf.sullivan/K352ApertureTestOnK20d As you move away from wide open (f2) to smaller apertures (f12.8), light moves toward overexposure. (You can see more light in the big shadow on the right.) This did the same with an M400/5.6 although I didn't post the details. All I can figure is that it has something to do with the aperture lever being linear. Since the A lenses (and later), the movement has been linear. With the earlier M and K lenses, the movement is non-linear. Is it possible that the K20D measures the right exposure, and then sets a matching A lens aperture, not closing the lens all the way down to the f12.8 we have set? Regards, Bob S. On Fri, May 9, 2008 at 8:56 PM, William Robb <[EMAIL PROTECTED]> wrote: > One of the guys on the Pentax Dysfunctional Web Forum chalenged me to test my > K20 exposure > system with manual aperture lenses (green button manual). > The camera failed miserably, over exposing by quite a large amount at all > f-stops but maximum > and minimum. > Would it be possible for some others of us to run the following test: > > Put a non A series lens onto their camera doesn't matter which, but it would > be nice to have > details, and run a series of exposures from maximum aperture to minimum > aperture to test the > linearity of the metering and perhaps report back. > > Sorry if this has been discussed before. > > I ran the test with several lenses, and then put an original equipment istD > screen into the K20 > as buddy thought that the screen itself was at fault, and insisted that it > had been a problem > with every DSLR since the istD. The screen was not the problem. > > Thanks > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
