             Directions for How To Find Display Gamma

Before viewing the gamma image dim the lights in the room and set the
monitor brightness and contrast to maximum.  While viewing a black screen,
lower the brightness gradually until the "background" is no longer
noticable (ie when it just fades from view).  This may be difficult
on monitors that use overscanning, unless you change the viewable
area settings.

Now, lower the contrast until the alternating white and black bars
on the left edge of each column are equal in width.  This is trying
to get a 50% gray by using half white and half black.  If this is
not possible, choose a contrast setting which is about in the middle.
While viewing the image from a distance, or with squinted eyes, one
of the numbered "swatches" will best match the gray value approximated
by the white and black bars.  The number in this "swatch" is your
display's actual gamma value.

Normal display gamma values are in the range 2.0 to 2.6, and the commonly
accepted value for most monitors is 2.2.  If your monitor is usually used
in a dim environment, we often use a gamma value that is 15% - 25% lower
than the actual display gamma to give the images more contrast.  Some
systems, such as Macs and SGIs, already do gamma correction, so they may
have display gammas of 1.0 or 1.8.

Whatever display gamma that you determine is that of your monitor
should be set in your povray.ini file with the statement:

Display_Gamma = 2.2

or whatever your actual gamma value is.




