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On Sunday 22 June 2008 10:23:31 jay chen wrote:
> Could someone tell me what the difference between field of
> view and bounding box is? Any suggestions and comments are
> appreciated.
The field of view (FOV) relates to *image scale*. This can be measured in one
of several ways. In an optical system the FOV is a function of the effective
focal length of the optical system multipled by the linear extent of the
image frame. So to give an example: the image scale in degrees per mm is
approximated by the formula 57.3/F, where F is measured in millimeters. This
means the image scale of a 50mm focal length lens is 57.3/50 = 1.46 deg/mm
and if the image extends over the full 35mm frame (which is 36mm x 24mm) it
covers a rectangular area of angular size 41.2deg x 27.5deg. If your bounding
box overlayed on an image generated by that optical system was 36mm x 24mm
then angular extent of the image would therefore cover 41.2deg x 27.5deg.
The bounding box calibrated in mm, or pixels or whatever linear scale you are
using is independent of the image scale, but can be calibrated for your
optical system so one knows the extent of the area being picked out.
Hope this helps,
Dave Randell
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