Luster versus light: ground, size, power and movement
Highlights on spheres and quicksilver; why luster travels with the eye
Continuing the section on luster, this page gathers four chapters. Chapter 773 states that a highlight on a whiter ground is of lesser splendour; chapter 774 that on spheres equally distant from the eye the smaller sphere yields the smaller highlight, citing the tiny grains of quicksilver whose lusters equal the grains themselves because the pupil's visual power exceeds them. Chapters 775 and 776 distinguish luster from light: luster is always more intense but smaller, and it moves with the eye or its cause, whereas light is fixed to its place while its cause holds still. The sheet is continuous text with no drawing.
On this page
A highlight shrinks with the size of the sphere
Chapter 774 holds that on spheres equally distant from the eye the smaller sphere carries the smaller highlight. Leonardo cites the little grains of quicksilver, almost imperceptible in size, whose lusters equal the grains themselves because the visual power of the pupil exceeds the grain and surrounds it.
The difference between luster and light
Chapter 775 explains that luster is always more powerful than light, while light is of greater extent than luster. Luster moves together with the eye or with its cause, whereas light stays fixed to its determined place so long as the cause that generates it does not move.
A highlight on a white ground has little power
Chapter 773 states that among lusters of equal power the one generated on a whiter surface shows itself of lesser splendour. The opening lines tie this to the earlier point that a highlight differs most from a black ground.