Originally posted by vonBaloney That's what I would figure, but why would it be a problem the other way around on a modern camera if you are using it the same way? If I am using a K or M lens on a DSLR, that means I'll be in M mode metering with the green button, which actually stops down to take a reading (so that should be accurate). It is actually using 'A' lenses normally where it is guesstimating exposures that I'd expect to see some inaccuracies, or using K/M lenses on older cameras with non-crippled mounts where it was essentially doing the same thing mechanically instead of electronically.
See my edit note to my post. I spent a long time looking into this, and found for example, the K10 screen, which is identical size to then*istD had horrible non linearity in K lens metering, but when I put the *istD screen into the K10 it was almost perfect (like the *istD)
I think it is a function of the way light hits the screen, and the impact of the scatter off the screen, as it hits the metering segments, that causes the issue.