If values in a gradation are correct but the painting still looks flat, which element may be lacking?

Correct answer: Variety of edges and colour temperature contrast

The governing concept is that depth is created by several visual relationships, not value alone. Varied edges—some soft, some firm—and warm or cool temperature shifts can separate planes, suggest atmosphere and describe turning form even when the light-dark gradation is correct. Paper size and brush price do not create depth, while simply increasing the number of colours may add noise. Thus A is the most useful correction.