This is about using the SL with its bespoke AF lenses, e.g., the 24-90: when composing and (auto-) focusing in aperture priority mode, is the iris wide-open, then stops down to the selected aperture at exposure, and opens up again afterward for the next shot, a la film SLRs? Hard to tell when you're behind the camera, and the SL IB is mute on the subject. Stan Yoder