File: gamma.gif
Size: 15055
Date: Mar 4, 1996
Time: 16:30
Author: Andreas Dilger
AuthorEmail: adilger@enel.ucalgary.ca
Uploader: Andreas Dilger
UploaderEmail:  adilger@enel.ucalgary.ca
Short: Test image for finding display gamma for POV 3.0
SuggestedDirectory:  None - to be included in final POV 3.0 release?
OperatingSystems:  N/A
 
             Directions for How To Find Display Gamma

Before viewing the gamma image darken 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.  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.