Third time i'm writing this post, this board software is annoying...
I started by mapping the set/get_focus values to GetFocusLensCurrentPosition. See attached file.
This creates just more confusion:
1. Between set_focus 0 and 10 the camera will assume the same focus position, get_focus returns a nonsensical 37 while GetFocusLensCurrentPosition returns 1352. This is already less than the cameras Autofocus in macro mode can achieve, which is about 1420 or about 1 cm in front of the lens.
I suppose nobody has noticed because the difference is negligible at that distance.
2. Between set_focus 10 and 16 GetFocusLensCurrentPosition changes as expected while get_focus returns more nonsense. Only at set_focus 17 do things start to make sense overall.
Since this only affects the very near field (below 1cm at zoom level 0, below ~1 meter at max zoom) it might be sufficient to map the area where GetFocusLensCurrentPosition correlates nicely with a subject distance and "guess" or extrapolate for the areas where it doesnt.
It wont be all too accurate, but i dont think anybody is expecting any level of accuracy from those crappy little cameras.
Besides, i dont get the need for setting a subject distance in cm anyways. I can only gauge the distance to the subject very roughly by eye and i wont get out my tape measure any time i set manual focus. So its something of a guessing game anyways.
What would be infinitely more helpful would be being able to force on the AF Zoom which magnifies a part of the frame in the middle to help confirm focusing.
Unfortunately on the ixus 160 that zoom thing is available, but only comes on after the camera has autofocused on its own successfully.