Does anyone know about the CAM_HAS_ND_FILTER setting.
AFAIK the SX20 doesn't have a ND (Neutral density) filter. (
[1])
The IXUS series and the cheaper A series cameras use a ND filter instead of a "real" aperture (diaphragm iris),
other Powershots with a "real" aperture - all the cameras with an Av mode - don't have an additional ND filter;
only some of the more expensive models from the G series are equipped with both, a iris diaphragm and a ND filter.
NR (noise reduction) isn't related to the ND filter...