Proof that a receding light loses splendour, not size
The sun's image on water; a luminant tested at two distances (r g and h L)
The folio opens by noting that the sun's reflected image on water throws out rays, within and beyond the water, that illuminate at a distance as if it were a real flame. Leonardo asks why a candle withdrawn from the eye dims in brightness yet not in apparent size. A funnel-shaped diagram labelled n m, a c o b, r g and h L shows a luminant at two distances: nearer (r g) it impresses the eye's light strongly over a b, farther (h L) only over the smaller c o. He concludes that the power of the splendour falls while the quantity does not.
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The sun's image on water lights like a real flame
The reflected image of the sun on water casts rays inside and outside the water that carry light a long way, as though it were a real flame. Leonardo then asks why a candle carried far off loses brightness to the eye yet not its apparent size.
A luminant compared at two distances in the eye
The illuminant r g makes a stronger impression on the eye's light n m a b at the near site a b than when withdrawn to h L, whose impression falls only on the smaller region c o. The power of the splendour is thereby lessened, but not the quantity, since the base of the light is touched alike by the smaller image c o and the greater image a b.