If pressing one button is so easy, why don't we press a button to change aperture? Sometimes pressing one button is too much work. Ergonomics are important, otherwise I'd be shooting another brand of camera.
There are two dials in aperture priority. The back one should be configurable to change the ISO, like on the D90 (Show ISO/Easy ISO).
There are two dials in aperture priority. The back one should be configurable to change the ISO, like on the D90 (Show ISO/Easy ISO).