have you took into consideration that the light adapts to have a better chance to go through. or better yet the shaders themselves alter the light wavelengths as it pass thought. this will show that after the first shade the second is at such a shift (90Ã‚Â°) that light has only a 50% chance to pass though. but if you add a 3rd at 45Ã‚Â° it alters light to give it a better chance to pass through.