The Notebooks

OF PAINTING. The surface of every opaque body assumes the hues reflected from surrounding objects. The surface of an opaque body assumes the hues of surrounding objects more strongly in proportion as the rays that form the images of those objects strike the surface at more equal angles. And the surface of an opaque body assumes a stronger hue from the surrounding objects in proportion as that surface is whiter and the colour of the object brighter or more highly illuminated. 270. OF THE RAYS WHICH CONVEY THROUGH THE AIR THE IMAGES OF OBJECTS. All the minutest parts of the image intersect each other without interfering with each other. To prove this let _r_ be one of the sides of the hole, opposite to which let _s_ be the eye which sees the lower end _o_ of the line _n o_. The other extremity cannot transmit its image to the eye _s_ as it has to strike the end _r_ and it is the same with regard to _m_ at the middle of the line. The case is the same with the upper extremity _n_ and the eye _u_. And if the end _n_ is red the eye _u_ on that side of the holes will not see the green colour of _o_, but only the red of _n_ according to the 7th of this where it is said: Every form projects images from itself by the shortest line, which necessarily is a straight line, &c. [Footnote: 13. This probably refers to the diagram given under No. 66.] 271. OF PAINTING. The surface of a body assumes in some degree the hue of those around it. The colours of illuminated objects are reflected from the surfaces of one to the other in various spots, according to the various positions of those objects. Let _o_ be a blue object in full light, facing all by itself the space _b c_ on the white sphere _a b e d e f_, and it will give it a blue tinge, _m_ is a yellow body reflected onto the space _a b_ at the same time as _o_ the blue body, and they give it a green colour (by the 2nd [proposition] of this which shows that blue and yellow make a beautiful green &c.) And the rest will be set forth in the Book on Painting. In that Book it will be shown, that, by transmitting the images of objects and the colours of bodies illuminated by sunlight through a small round perforation and into a dark chamber onto a plane surface, which itself is quite white, &c. But every thing will be upside down. Combination of different colours in cast shadows. 272. That which casts the shadow does not face it, because the shadows are produced by the light which causes and surrounds the shadows. The shadow caused by the light _e_, which is yellow, has a blue tinge, because the shadow of the body _a_ is cast upon the pavement at _b_, where the blue light falls; and the shadow produced by the light _d_, which is blue, will be yellow at _c_, because the yellow light falls there and the surrounding background to these shadows _b c_ will, besides its natural colour, assume a hue compounded of yellow and blue, because it is lighted by the yellow light and by the blue light both at once. Shadows of various colours, as affected by the lights falling on them. That light which causes the shadow does not face it. [Footnote: In the original diagram we find in the circle _e_ "_giallo_" (yellow) and the cirle _d_ "_azurro"_ (blue) and also under the circle of shadow to the left "_giallo_" is written and under that to the right "_azurro_". In the second diagram where four circles are placed in a row we find written, beginning at the left hand, "_giallo_" (yellow), "_azurro_" (blue), "_verde_" (green), "_rosso_" (red).] The effect of colours in the camera obscura (273-274). 273. The edges of a colour(ed object) transmitted through a small hole are more conspicuous than the central portions. The edges of the images, of whatever colour, which are transmitted through a small aperture into a dark chamber will always be stronger than the middle portions. 274. OF THE INTERSECTIONS OF THE IMAGES IN THE PUPIL OF THE EYE. The intersections of the images as they enter the pupil do not mingle in confusion in the space where that intersection unites them; as is evident, since, if the rays of the sun pass through two panes of glass in close contact, of which one is blue and the other yellow, the rays, in penetrating them, do not become blue or yellow but a beautiful green. And the same thing would happen in the eye, if the images which were yellow or green should mingle where they [meet and] intersect as they enter the pupil. As this does not happen such a mingling does not exist. OF THE NATURE OF THE RAYS COMPOSED OF THE IMAGES OF OBJECTS, AND OF THEIR INTERSECTIONS. The directness of the rays which transmit the forms and colours of the bodies whence they proceed does not tinge the air nor can they affect each other by contact where they intersect. They affect only the spot where they vanish and cease to exist, because that spot faces and is faced by the original source of these rays, and no other object, which surrounds that original source can be seen by the eye where these rays are cut off and destroyed, leaving there the spoil they have conveyed to it. And this is proved by the 4th [proposition], on the colour of bodies, which says: The surface of every opaque body is affected by the colour of surrounding objects; hence we may conclude that the spot which, by means of the rays which convey the image, faces--and is faced by the cause of the image, assumes the colour of that object. On the colours of derived shadows (275. 276). 275. ANY SHADOW CAST BY AN OPAQUE BODY SMALLER THAN THE LIGHT CAUSING THE SHADOW WILL THROW A DERIVED SHADOW WHICH IS TINGED BY THE COLOUR OF THE LIGHT. Let _n_ be the source of the shadow _e f_; it will assume its hue. Let _o_ be the source of _h e_ which will in the same way be tinged by its hue and so also the colour of _v h_ will be affected by _p_ which causes it; and the shadow of the triangle _z k y_ will be affected by the colour of _q_, because it is produced by it. [7] In proportion as _c d_ goes into _a d_, will _n r s_ be darker than _m_; and the rest of the space will be shadowless [11]. _f g_ is the highest light, because here the whole light of the window _a d_ falls; and thus on the opaque body _m e_ is in equally high light; _z k y_ is a triangle which includes the deepest shadow, because the light _a d_ cannot reach any part of it. _x h_ is the 2nd grade of shadow, because it receives only 1/3 of the light from the window, that is _c d_. The third grade of shadow is _h e_, where two thirds of the light from the window is visible. The last grade of shadow is _b d e f_, because the highest grade of light from the window falls at _f_. [Footnote: The diagram Pl. III, No. 1 belongs to this chapter as well as the text given in No. 148. Lines 7-11 (compare lines 8-12 of No. 148) which are written within the diagram, evidently apply to both sections and have therefore been inserted in both.] 276. OF THE COLOURS OF SIMPLE DERIVED SHADOWS. The colour of derived shadows is always affected by that of the body towards which they are cast. To prove this: let an opaque body be placed between the plane _s c t d_ and the blue light _d e_ and the red light _a b_, then I say that _d e_, the blue light, will fall on the whole surface _s c t d_ excepting at _o p_ which is covered by the shadow of the body _q r_, as is shown by the straight lines _d q o e r p_. And the same occurs with the light _a b_ which falls on the whole surface _s c t d_ excepting at the spot obscured by the shadow _q r_; as is shown by the lines _d q o_, and _e r p_. Hence we may conclude that the shadow _n m_ is exposed to the blue light _d e_; but, as the red light _a b_ cannot fall there, _n m_ will appear as a blue shadow on a red background tinted with blue, because on the surface _s c t d_ both lights can fall. But in the shadows only one single light falls; for this reason these shadows are of medium depth, since, if no light whatever mingled with the shadow, it would be of the first degree of darkness &c. But in the shadow at _o p_ the blue light does not fall, because the body _q r_ interposes and intercepts it there. Only the red light _a b_ falls there and tinges the shadow of a red hue and so a ruddy shadow appears on the background of mingled red and blue. The shadow of _q r_ at _o p_ is red, being caused by the blue light _d e_; and the shadow of _q r_ at _o' p'_ is blue being caused by the red light _a b_. Hence we say that the blue light in this instance causes a red derived shadow from the opaque body _q' r'_, while the red light causes the same body to cast a blue derived shadow; but the primary shadow [on the dark side of the body itself] is not of either of those hues, but a mixture of red and blue. The derived shadows will be equal in depth if they are produced by lights of equal strength and at an equal distance; this is proved. [Footnote 53: The text is unfinished in the original.] [Footnote: In the original diagram Leonardo has written within the circle _q r corpo obroso_ (body in shadow); at the spot marked _A, luminoso azzurro_ (blue luminous body); at _B, luminoso rosso_ (red luminous body). At _E_ we read _ombra azzurra_ (blue tinted shadow) and at _D ombra rossa_ (red tinted shadow).] On the nature of colours (277. 278). 277.