n. Delicate variations of light and shade on a photograph.n. The act of one who tones, in any sense; specifically, in photography, the method or the art of tinting or coloring pictures by chemical means, to give them an agreeable tone or color; especially, the treatment of silver positive prints or transparencies in a bath which consists most commonly of a very weak solution of chlorid of gold in combination with other chemicals, to give a more pleasing color and also greater permanency to the picture.