Instead, they refer to the fir's evergreen quality as a symbol of constancy and faithfulness. Philosophies of mind explore whether objectivity relies on perceptual constancy. Symbolizes loyalty, constancy, and righteousness. The sapphire is recognized as a symbol of truth, sincerity, and constancy. Black is indicative of determination and constancy. Some consider the "principle of the constancy of the velocity of light" insufficiently substantiated. The degree of accuracy and constancy of cooking temperature required varies with the food cooked. Color constancy is achieved by chromatic adaptation. The phenomenon of color constancy occurs when the source of illumination is not directly known. Examples were the constancy of the speed of light, time dilation, length contraction. Blue for the firmament, truth, and constancy. This constancy is usually accomplished by changes in gait. Color balance is also related to color constancy. The term C-value reflects this observed constancy. There are two possible mechanisms for color constancy.