The m4/3rds lenses stay with their iris at the chosen position (say, f/11). While trying to make a photo, for the AF to function effectively, they open wide. After AF is achieved or the shutter is tripped, they close down to the aperture and a picture is taken (even in full manual mode this happens with the system lenses from Pana and Oly)
All auto reflex cameras (SLRs and DSLRs) keep the diaphram fully open and it stops down only when the picture is about to be captured.
The aperture scenario:
Auto reflex SLR:
Why must this delay happen? Shouldn't Pana and Oly change this?