Nokia Lumia :: 710 Turned Off Brightness Auto Adjustment

I have already turned off the brightness auto adjustment, however I still notice the screen brightness change slightly when there is movement on screen, for example when you use finger touch and move on the screen. ( very noticeable when background is white).I tried to live with it however find it very annoying when you play on a white background game. Like the free game Penguin ( which is similar to Tiny Wing on iOS).