Well i check on my camera and uder the metering/exposure option, center ewighted is at 8mm
i also have an issue even with a black felt background with the whites and yellow
This guy has some pretty vivid Yellows but they dont show so well i took probably 20 photos before getting this one
http://i25.photobucket.com/albums/c63/mybuicksfaster/Leopard%20geckos%20for%20sale/HHYM1.jpg