If, however, I bring it near the window, and let the sun fall on a part of it, I at once recognize that what I have been seeing is not white, but a decided grey.
Similarly, when I look at a brick viaduct a mile or two off, I appear to myself to recognize its redness.

In fact, however, the impression of colour which I receive from the object is not that of brick-red at all, but a much less decided tint; which I may easily prove by bending my head downwards and letting the scene image itself on the retina in an unusual way, in which case the recognition of the object as a viaduct being less distinct, I am better able to attend to the exact shade of the colour.
Nowhere is this inattention to the sensation of the moment exhibited in so striking a manner as in pictorial art.

A picture of Meissonier may give the eye a representation of a scene in which the objects, as the human figures and horses, have a distinctness that belongs to near objects, but an apparent magnitude that belongs to distant objects.

So again, it is found that the degree of luminosity or brightness of a pictorial representation differs in general enormously from that of the actual objects.

Thus, according to the calculations of Helmholtz,[44] a picture representing a Bedouin's white raiment in blinding sunshine, will, when seen in a fairly lit gallery, have a degree of luminosity reaching only to about one-thirtieth of that of the actual object.