Few subjects are dominated by one color component, so autoexposure usually works well. For example, blue sky appears blue, but actually there is good deal of white mixed with the blue. Flowers are an exception. Flowers can have very pure colors. White flowers or pastel shades do not pose a problem. Usually it is red or red-orange flowers that create a problem. … The rule of thumb for subjects having pure colors is to force the exposure to one and a half stops below the automatic determination.

