On my Pentax ME Super with a legacy lens (Pentax SMC 50mm 1.7) my camera meters at all aperture ring settings. Yet, if I transfer this lens to a modern Pentax DSLR, I need to stop down the lens to meter properly. By pressing the stop-down button, the camera closes the aperture blades to the selected aperture, and then reads the reduced light amount.
I find this behaviour annoying and wish that modern Pentax cameras can meter a legacy lens without having to do the stop down procedure. I have read elsewhere that this is because modern cameras do open-aperture metering. However, can't we keep the metering behaviour of old cameras with respect to legacy lenses?