which is one of the problems with film or digital (typically linear). Your eyes have an extremely large dynamic range compared to any man made image capture devices. In a particular view the dynamic range is supposed to be around 10 stops ( a luminance ratio of about 1:1000), but in total dynamic range (eyes adjusted to scene) the range is better than 40 stops or a ratio of 1 to 100 trillion in luminance. Not a bad facility. So full moon luminance isn't all that bright - its just that your eyes are that good.