The limiting factor here is likely image quality (the live view image is not that good, especially if there's not enough light).
Thanks, Fudgey, I suspect that you have hit the nail dead centre on the head here, and that this is why my suggestion probably would not work in my circumstances, even if such a facility did exist.
I am normally working indoors in such poor light (typically requiring around a 4 second exposure) that the camera's autofocus is not reliable, and that is why I would prefer to focus manually. Presumably it is for the same reason that I also find the manual focus enlarged area difficult to use, and on reflection I suspect that by the same token noise levels in the live image would make it unlikely that my suggestion would work.
So I must take a different approach. Because I can almost always accurately measure the distance between the camera and my subject matter, I intend to equate the possible range of set_focus distances (576 to 65535 on the G9 at full telephoto) to actual distances. To make life easy in doing this I propose to mount a supplementary close up lens over the G9's lens and photograph along the length of a steel tape measure at different values of set_focus. If I know (a) the angle between the camera's optical axis and the tape measure, and (b) the strength of the close up lens in dioptres, it is a matter of simple math to calculate the true distances the camera would be focused on without the supplementary lens. I can then create a table or graph of set-focus values against camera to subject distances.
Does this seem reasonable?
Regards
Andrew
