Optical study: rays converging on a circle (a, a, b)
Ruled lines from labelled points a, a and b meeting a circle at the right
A ruled optical diagram fills the upper part of the sheet: straight lines run from points marked a, a and b toward a circle at the right, where they converge as though upon an eye or lens. A further point appears lettered d at the left of the construction, and fainter lines repeat the figure below. Only the labels a - a - b are transcribed.
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Rays converging on a circle at a, a, b
Lines drawn from the labelled points a, a and b meet at a circle on the right of the sheet, the geometry Leonardo uses for rays of light or lines of sight gathering upon an eye. A point d also lies at the left, though it is not part of the transcription.