I say that the reason that objects appear diminished in size is
because they are remote from the eye; this being the case it is
evident that there must be a great extent of atmosphere between the
eye and the objects, and this air interferes with the distinctness
of the forms of the object. Hence the minute details of these
objects will be indistinguishable and unrecognisable. Therefore, O
Painter, make your smaller figures merely indicated and not highly
finished, otherwise you will produce effects the opposite to nature,
your supreme guide. The object is small by reason of the great
distance between it and the eye, this great distance is filled with
air, that mass of air forms a dense body which intervenes and
prevents the eye seeing the minute details of objects.
569.
Whenever a figure is placed at a considerable distance you lose
first the distinctness of the smallest parts; while the larger parts
are left to the last, losing all distinctness of detail and outline;
and what remains is an oval or spherical figure with confused edges.
570.