Nature is interesting at all times, but, as a general rule, very harsh and glaring sunlight, when the sun is high in the heavens, should be avoided, … - Arthur Hammond

A small but noticeable patch of contrasting light or dark tone would more correctly be described as an accent than as a mass, and it will be found that, as a rule, an accent is needed to prevent a picture from becoming monotonous and uninteresting.

Where light falls on an object and is reflected back to the eye, we see a highlight; where it strikes at an angle and is reflected back other than directly to the eye we see halftones; where no direct light falls on the object we have shadows: and these highlights, halftones and shadows are modified by light reflected into them by other objects and by other parts of the same object.

...picture-making is almost entirely a matter of good taste, and that is largely instinctive when the taste has been trained and cultivated.