An adaptive fill-flash technique for digital photography that employs
flash and no-flash image pairs. A flash image, captured using a flash of
known characteristics and ambient light, and an ambient light image,
which is taken with only ambient light, of the same image subject matter
are acquired. A flash only image, computed by subtracting the known
ambient light image from the flash and ambient light image, is computed.
The flash only image and the ambient light image are then each white
balanced to the flash light and the ambient light, respectively, to form
two white-balanced images. These two white-balanced images are then added
to form a white balanced image, I, in which the flash and ambient light
color agree. It is also possible to reduce the hot spots in image I, and
adjust flash strength.