Originally posted by MADDSNIPER Im sure someone else will come along in a bit and give you a detailed answer but off the top of my head I think old glass has to be in M mode otherwise it will shoot everything fully wide open no matter what you try to set the aperture to.
"A series" lenses meter wide open on the digital bodies and do not need a stop down (green button) step.
However A lenses do see to over/underexpose at times. The M (stop down) method seems a little more accurate but more troublesome to me.
OP: Was this with the same lens or different lenses when you saw the same exposure listed but diffeent results?
Remember that the A setting has the camera press the aperture level to an approximation of the f/stop using a formula, the M method uses preset f/stops and the camera just has to swtich (on/off0 vs. the precision needed for A lenses..