HOW A PAINTER SHOULD CARRY OUT THE PERSPECTIVE OF COLOUR IN
PRACTICE.

In order to put into practice this perspective of the variation and
loss or diminution of the essential character of colours, observe at
every hundred braccia some objects standing in the landscape, such
as trees, houses, men and particular places. Then in front of the
first tree have a very steady plate of glass and keep your eye very
steady, and then, on this plate of glass, draw a tree, tracing it
over the form of that tree. Then move it on one side so far as that
the real tree is close by the side of the tree you have drawn; then
colour your drawing in such a way as that in colour and form the two
may be alike, and that both, if you close one eye, seem to be
painted on the glass and at the same distance. Then, by the same
method, represent a second tree, and a third, with a distance of a
hundred braccia between each. And these will serve as a standard and
guide whenever you work on your own pictures, wherever they may
apply, and will enable you to give due distance in those works. [14]
But I have found that as a rule the second is 4/5 of the first when
it is 20 braccia beyond it.

[Footnote: This chapter is one of those copied in the Manuscript of
the Vatican library Urbinas 1270, and the original text is rendered
here with no other alterations, but in the orthography. H. LUDWIG,
in his edition of this copy translates lines 14 and 15 thus: "_Ich
finde aber als Regel, dass der zweite um vier Funftel des ersten
abnimmt, wenn er namlich zwanzig Ellen vom ersten entfernt ist
(?)"_. He adds in his commentary: "_Das Ende der Nummer ist wohl
jedenfalls verstummelt_". However the translation given above shows
that it admits of a different rendering.]

The rules of aerial perspective (295--297).