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.