The G12 does not have a continuous focus motor - there are only a discrete number of focus positions available.
Depending on your starting position +10mm will not change the actual focus distance.
This has nothing to do with the G12 or not having a continuous focus motor, it is completely normal behaviour based on the lens equations.
Quite simply, it is the focus stepper motor that can only move a certain distance.
(that can actually be a fraction of the steppers native step, doubt if that is done on cameras).
For each change of stepper position, you calculate an assumed focus distance, it is unlikely to be a 'nice' round number.
Small sensor digital cameras with short focal length lenses have tremendous depth of field, especially at wide angle.
Starting at 10mm, a single step may correspond to a 1mm change of focused distance.
That soon changes to 3mm, 10mm, 100mm etc.
After about one or two metres with the wide-angle lens, the depth of field already extends to infinity.
The next step takes you to 65535mm , in Canon and CHDK terms.
Focus at 10mm and try bracketing again.
Even better, zoom to next setting and start at whatever near focus applies.
You should then see focus change.
David
