The Notebooks of Leonardo Da Vinci/V
V. Theory of colours.
_Leonardo's theory of colours is even more intimately connected with his principles of light and shade than his Perspective of Disappearance and is in fact merely an appendix or supplement to those principles, as we gather from the titles to sections_ 264, 267_, and _276_, while others again_ (_Nos._ 281, 282_) are headed_ Prospettiva.
_A very few of these chapters are to be found in the oldest copies and editions of the Treatise on Painting, and although the material they afford is but meager and the connection between them but slight, we must still attribute to them a special theoretical value as well as practical utility--all the more so because our knowledge of the theory and use of colours at the time of the Renaissance is still extremely limited._
The reciprocal effects of colours on objects placed opposite each other (263-272).
The hue of an illuminated object is affected by that of the luminous body.
The surface of any opaque body is affected by the colour of surrounding objects.
A shadow is always affected by the colour of the surface on which it is cast.
An image produced in a mirror is affected by the colour of the mirror.
OF LIGHT AND SHADE.
Every portion of the surface of a body is varied [in hue] by the [reflected] colour of the object that may be opposite to it.
If you place a spherical body between various objects that is to say with [direct] sunlight on one side of it, and on the other a wall illuminated by the sun, which wall may be green or of any other colour, while the surface on which it is placed may be red, and the two lateral sides are in shadow, you will see that the natural colour of that body will assume something of the hue reflected from those objects. The strongest will be [given by] the luminous body; the second by the illuminated wall, the third by the shadows. There will still be a portion which will take a tint from the colour of the edges.
The surface of every opaque body is affected by the colour of the objects surrounding it. But this effect will be strong or weak in proportion as those objects are more or less remote and more or less strongly [coloured].
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.
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.]
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.
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).
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.
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).
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.  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 . _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.]
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).
No white or black is transparent.
[Footnote 2: See Footnote 3] Since white is not a colour but the neutral recipient of every colour [Footnote 3: _il bianco non e colore ma e inpotentia ricettiva d'ogni colore_ (white is not a colour, but the neutral recipient of every colour). LEON BATT. ALBERTI "_Della pittura_" libro I, asserts on the contrary: "_Il bianco e'l nero non sono veri colori, ma sono alteratione delli altri colori_" (ed. JANITSCHEK, p. 67; Vienna 1877).], when it is seen in the open air and high up, all its shadows are bluish; and this is caused, according to the 4th [prop.], which says: the surface of every opaque body assumes the hue of the surrounding objects. Now this white [body] being deprived of the light of the sun by the interposition of some body between the sun and itself, all that portion of it which is exposed to the sun and atmosphere assumes the colour of the sun and atmosphere; the side on which the sun does not fall remains in shadow and assumes the hue of the atmosphere. And if this white object did not reflect the green of the fields all the way to the horizon nor get the brightness of the horizon itself, it would certainly appear simply of the same hue as the atmosphere.
On gradations in the depth of colours (279. 280).
Since black, when painted next to white, looks no blacker than when next to black; and white when next to black looks no whiter than white, as is seen by the images transmitted through a small hole or by the edges of any opaque screen ...
Of several colours, all equally white, that will look whitest which is against the darkest background. And black will look intensest against the whitest background.
And red will look most vivid against the yellowest background; and the same is the case with all colours when surrounded by their strongest contrasts.
On the reflection of colours (281-283).
Every object devoid of colour in itself is more or less tinged by the colour [of the object] placed opposite. This may be seen by experience, inasmuch as any object which mirrors another assumes the colour of the object mirrored in it. And if the surface thus partially coloured is white the portion which has a red reflection will appear red, or any other colour, whether bright or dark.
Every opaque and colourless body assumes the hue of the colour reflected on it; as happens with a white wall.
That side of an object in light and shade which is towards the light transmits the images of its details more distinctly and immediately to the eye than the side which is in shadow.
The solar rays reflected on a square mirror will be thrown back to distant objects in a circular form.
Any white and opaque surface will be partially coloured by reflections from surrounding objects.
[Footnote 281. 282: The title line of these chapters is in the original simply _"pro"_, which may be an abbreviation for either _Propositione_ or _Prospettiva_--taking Prospettiva of course in its widest sense, as we often find it used in Leonardo's writings. The title _"pro"_ has here been understood to mean _Prospettiva_, in accordance with the suggestion afforded by page 10b of this same MS., where the first section is headed _Prospettiva_ in full (see No. 94), while the four following sections are headed merely _"pro"_ (see No. 85).]
WHAT PORTION OF A COLOURED SURFACE OUGHT IN REASON TO BE THE MOST INTENSE.
If _a_ is the light, and _b_ illuminated by it in a direct line, _c_, on which the light cannot fall, is lighted only by reflection from _b_ which, let us say, is red. Hence the light reflected from it, will be affected by the hue of the surface causing it and will tinge the surface _c_ with red. And if _c_ is also red you will see it much more intense than _b_; and if it were yellow you would see there a colour between yellow and red.
On the use of dark and light colours in painting (284--286).
WHY BEAUTIFUL COLOURS MUST BE IN THE [HIGHEST] LIGHT.
Since we see that the quality of colour is known [only] by means of light, it is to be supposed that where there is most light the true character of a colour in light will be best seen; and where there is most shadow the colour will be affected by the tone of that. Hence, O Painter! remember to show the true quality of colours in bright lights.
An object represented in white and black will display stronger relief than in any other way; hence I would remind you O Painter! to dress your figures in the lightest colours you can, since, if you put them in dark colours, they will be in too slight relief and inconspicuous from a distance. And the reason is that the shadows of all objects are dark. And if you make a dress dark there is little variety in the lights and shadows, while in light colours there are many grades.
Colours seen in shadow will display more or less of their natural brilliancy in proportion as they are in fainter or deeper shadow.
But if these same colours are situated in a well-lighted place, they will appear brighter in proportion as the light is more brilliant.
The variety of colours in shadow must be as great as that of the colours in the objects in that shadow.
Colours seen in shadow will display less variety in proportion as the shadows in which they lie are deeper. And evidence of this is to be had by looking from an open space into the doorways of dark and shadowy churches, where the pictures which are painted in various colours all look of uniform darkness.
Hence at a considerable distance all the shadows of different colours will appear of the same darkness.
It is the light side of an object in light and shade which shows the true colour.
On the colours of the rainbow (287. 288).
Treat of the rainbow in the last book on Painting, but first write the book on colours produced by the mixture of other colours, so as to be able to prove by those painters' colours how the colours of the rainbow are produced.
WHETHER THE COLOURS OF THE RAINBOW ARE PRODUCED BY THE SUN.
The colours of the rainbow are not produced by the sun, for they occur in many ways without the sunshine; as may be seen by holding a glass of water up to the eye; when, in the glass--where there are those minute bubbles always seen in coarse glass--each bubble, even though the sun does not fall on it, will produce on one side all the colours of the rainbow; as you may see by placing the glass between the day light and your eye in such a way as that it is close to the eye, while on one side the glass admits the [diffused] light of the atmosphere, and on the other side the shadow of the wall on one side of the window; either left or right, it matters not which. Then, by turning the glass round you will see these colours all round the bubbles in the glass &c. And the rest shall be said in its place.
THAT THE EYE HAS NO PART IN PRODUCING THE COLOURS OF THE RAINBOW.
In the experiment just described, the eye would seem to have some share in the colours of the rainbow, since these bubbles in the glass do not display the colours except through the medium of the eye. But, if you place the glass full of water on the window sill, in such a position as that the outer side is exposed to the sun's rays, you will see the same colours produced in the spot of light thrown through the glass and upon the floor, in a dark place, below the window; and as the eye is not here concerned in it, we may evidently, and with certainty pronounce that the eye has no share in producing them.
OF THE COLOURS IN THE FEATHERS OF CERTAIN BIRDS.
There are many birds in various regions of the world on whose feathers we see the most splendid colours produced as they move, as we see in our own country in the feathers of peacocks or on the necks of ducks or pigeons, &c.
Again, on the surface of antique glass found underground and on the roots of turnips kept for some time at the bottom of wells or other stagnant waters [we see] that each root displays colours similar to those of the real rainbow. They may also be seen when oil has been placed on the top of water and in the solar rays reflected from the surface of a diamond or beryl; again, through the angular facet of a beryl every dark object against a background of the atmosphere or any thing else equally pale-coloured is surrounded by these rainbow colours between the atmosphere and the dark body; and in many other circumstances which I will not mention, as these suffice for my purpose.