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Paris Manuscript F — 72

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Bibliothèque de l'Institut de France, Paris

Schema di sole visto dall'occhio, con:

f sole g - a b - c o m n d

Dimostrazione come la percussione de' razzi solari penetrati per li spiraculi son più luminosi in mezzo che dai lati, e la cagion di tale effetto.

Nel mezzo m è più luminoso, perché quivi vede tutto il corpo del sole, come mostran le linie m f e m g, che tocca[n] li lati dello spiraculo a b. E in o r vede mezzo il sole e in c d non ne vede parte alcuna di sole. Adunque v'è oscurissimo.

Figura analoga, con:

f g - a b - c m d

Ora diciamo che a b sia il foro minimo, ch'io ho fatto nella carta, per il quale io riguardo una stella o altro lume, e che c d sia la mia luce. Ora per guardare tale [s]tella pel foro a b la sua similitudine discende tutta in m ed è piccola, e se tal foro non s'interponessi in fra l'occhio e la stella, io vederei la stella tutta con tutta la luce c d come prima, ma mi pare maggiore, perché la vedo con maggiore potenzia, perché tutta la luce s'adopera in tal visione, come si vede per le 2 linie f c, g d.

Diagram of the sun seen by the eye, with:

f sun g - a b - c o m n d

Demonstration of how the percussion of the solar rays, penetrating through apertures, is more luminous in the middle than at the sides, and the cause of such an effect.

In the middle m it is more luminous, because there it sees the whole body of the sun, as the lines m f and m g show, which touch the sides of the aperture a b. And at o r it sees half the sun, and at c d it sees no part of the sun at all. Therefore it is darkest there.

Analogous figure, with:

f g - a b - c m d

Now let us say that a b is the minimal hole that I have made in the paper, through which I look at a star or other light, and that c d is my light [eye]. Now, to look at that star through the hole a b, its likeness descends entirely into m and is small; and if that hole were not interposed between the eye and the star, I would see the whole star with the whole light c d as before, but it appears larger to me, because I see it with greater power, since the whole light is employed in that vision, as is seen by the 2 lines f c, g d.

Why sunlight through an aperture is brightest at its centre

Solar rays strongest in the middle where the whole sun is seen; a star seen through a pinhole looks small

Optics & Light Astronomy

Leonardo demonstrates that solar rays passing through an aperture strike more brightly in the middle than at the sides: at the centre m the whole body of the sun is seen, as the lines m f and m g touching the aperture's sides a b show, while at o r only half the sun is seen and at c d none, so it is darkest there. An analogous figure treats a star viewed through a minimal hole a b made in paper: its likeness descends entirely into m and is small, whereas without the hole the star would be seen with the whole light c d and appear larger, because the full light is then employed, as the lines f c, g d show. Two cone-and-ray diagrams sit at the upper and lower right.

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Solar rays through an aperture are brightest at the centre (m, a b)

The percussion of solar rays penetrating through apertures is more luminous in the middle than at the sides. At the centre m it is brightest, because there the whole body of the sun is seen, as the lines m f and m g show, touching the aperture's sides a b; at o r half the sun is seen, and at c d none, so it is darkest there.

A star seen through a pinhole appears small (a b, c d, m)

Looking at a star through the minimal hole a b in paper, its likeness descends entirely into m and is small. Without the hole interposed, the star would be seen with the whole light c d and appear larger, because it is seen with greater power when the full light is employed, as the lines f c, g d show.

Reader's Edition — described with AI from the e-Leo transcription.