My take: J.C. is right when he says that K/M lenses are not "fully supported" by Pentax DSLRs. This is because "green-button metering" takes the meter reading when the lens is stopped down. Open aperture metering takes the meter reading with the lens wide open. "Green-button metering" takes in less light than open aperture metering. If you try to use "green-button metering" in low light with a small lens aperture, you might run out of the useful range of the meter.
On the other hand, "green-button metering"(also known as stop-down metering) may be more accurate than open-aperture metering because it takes the meter reading with the lens at the same aperture as will be used to actually take the picture. In addition, if you're shooting at or near wide open or in good light, the meter sensitivity issue is not likely to be a problem. A number of Pentax digital SLR users (includig myself) appear to be satisfied with the performance of "green-button metering". I personally find it easy to use and haven't had low-light metering problems since I typically shoot low-light images at or near wide-open anyway. J.C. seems to be very unhappy with "green-button metering". J.C. also seems to object to others' satisfaction with "green-button metering". I don't have a problem with J.C.'s dissatisfaction with "green-button metering", but I do find his objections to others' opinions annoying. Have a nice day. I'm going to go take some more pictures of my new daughter.... --Mark
