Now move the slider on the bottom to the right to
change the background color from light blue to
white. We can now see the rock with more accurate
colors. Simply save the new file and you have a
more accurate picture of the material.
The idea is to match a known color (white) in the
photo to a known color on your desktop. As I
mentioned in the first tutorial you can use this
same process with any picture where you know a
part of the picture is white. So it would work
with a stone with white inclusions for example
even if the background was black.
Note that the
other sliders in the program can be used also to
make minor adjustments but the main attribute to
fix will usually be the color temperature.