A quick test, pointing the camera at a lamp w/ a 135mm lens on it, showed that the metering pattern is significantly different from my F-1n. The F-1 has a rectangular patch in the center of the focus screen around the split prism, and that is apparently where it's metering pattern is. When I tested the F-1 w/ the lamp, that was pretty close. On the AT-1, the metering pattern, at least on this AT-1, is almost like a spot meter. It is much tighter, almost as if most of it's meter pattern was the split prism w/ fresnel circle in the center. Both have CDS meters I think, but the AT-1 is MUCH more sensitive to slight light changes. Of course, shooting film through it will tell the tale, but what I see looks very encouraging. I should probably ck the battery to see what's in there, but as it meters exactly w/ my handheld Sekonic, better to let sleeping dogs lie. Supposedly only the AT-1 requires an alkaline battery, whereas the AE-1, A-1, etc can use any old battery that supplies the proper voltage. I suspect the AT-1 can too.