--- ray/src/px/ra_pr.c	1990/03/12 15:14:40	1.8
+++ ray/src/px/ra_pr.c	1990/11/07 13:10:31	1.9
@@ -349,7 +349,7 @@ colormap  map;
 	register int  i, val;
 
 	for (i = 0; i < 256; i++) {
-		val = pow(i/256.0, 1.0/gamma) * 256.0;
+		val = pow((i+0.5)/256.0, 1.0/gamma) * 256.0;
 		map[0][i] = map[1][i] = map[2][i] = val;
 	}
 }