Photography itself may err by inaccurately rendering the relative tones in Nature. Then we shall have to ask, What is " Tone "?... - Alfred Horsley Hinton

… to put it into slightly different form, it is not the facts in nature that the good picture aims at portraying, but the effects of light and shade accompanied by a pleasing arrangement.

In selecting our subject…there are two factors which it should be borne in mind are essential, and these are Expression and Composition

...strictly speaking, tone is the relative lightness and darkness due to the effect of light governed by atmosphere, and has nothing to do with the relative lightness and darkness or relative value with which various colours appear when compared with each other.