These are all relatively close, and the mix of deep shadow and bright light is a tough test for center weighted metering. Paul On May 10, 2008, at 12:03 AM, Bob Sullivan wrote: > 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.
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