One thing, if I set Override Subj. Di. from the chdk menu
to 52 in rec mode, take a shot, then switch to play mode,
the 52 now becomes 101.
No big deal but I find this odd.
How you can see override values in play mode? 101 is the subject distance from plane equivalent from 52 on zoom(0).
some comments for subject distance:
1. canon internal _GetFocusLensSubjectDistance() equal to PROPCASE_SUBJECT_DIST1 and PROPCASE_SUBJECT_DIST2 (here named SD_Plane for subject distance from plane)
2. for camera user _GetFocusLensSubjectDistanceFromLens() for script commands get_focus(), set_focus(), distance overrides and DOF calculator equal to MF gauge (here named SD_Lens for subject distance from lens)
The difference between SD_Plane and SD_Lens is shooting_get_lens_to_focal_plane_width() (here named LP_Width). This value is dependent from zoom position.
- trunk 295: add MAX_DIST as infinity distance for SD_Plane
- trunk 1570: add INFINITY_DIST to mark infinity for sd override
- Find MIN_DIST, MAX_DIST in context SD_Plane
MIN_DIST = lowest possible value for SD_Plane on zoom(0)
MAX_DIST = greatest possible value for SD_Plane on zoom(zoom_steps-1) for detect INFINITY_DIST
- trunk 1690: add new DOF calculator by using SD_Lens context. MAX_DIST and sd override are in SD_Plane context.
- trunk 1719: switch sd override from SD_Plane to SD_Lens context
A590 use MIN_DIST=51 in SD_Lens context, MAX_DIST=65535 in SD_Plane context and no infinity detection possible
code in SD_Plane context
- MAX_DIST, INFINITY_DIST on generic/wrapper.c lens_set_focus_pos()
- gui.c > line 2453: conf.subj_dist_override_value = MAX_DIST, need SD_Plane context for shooting_get_subject_distance_override_value()
code in SD_Lens context
- MAX_DIST on DOF calculator
- MIN_DIST, MAX_DIST on shooting_subject_distance_bracketing()
- MIN_DIST on gui_subj_dist_override_value_enum()
A good solution is using MIN_DIST, MAX_DIST in SD_Lens context. For SD_Plane context we add LP_Width -> MIN_PLANE_DIST = MIN_DIST + LP_Width, MAX_PLANE_DIST = MAX_DIST + LP_Width. The infinity detection is not perfect for small zoom positions, but in any case there is a valid maximum for SD_Plane context.