Well when you press the green button, the aperture would stop down to its mechanical setting, a meter reading would be taken, which would allow the system to calculate the aperture based on the current ISO setting and the ratio of the EVs stopped down and wide open. Now you "save" the value of the aperture and use that virtual setting everytime you take a new picture, hence a new EV reading (note wide open) so with the EV ratio can't it be used to estimate what the speed will be when the pic is taken stopped down?
OK, so that gives you the relative aperture not the absolute one, but that's all you need.
The advantage is that you only have to press the green button when you change the aperture, not everytime the light changes. Like real Aperture priority. Please feel free to tell me where the flaw is, because I'm just speculating. :)
Right, you've sold me on the idea - I think it would be a useful addition to the current hyper-manual behaviour. :-)
S
