perspective (linear vs. retinal)

via Panofsky, i find this charming observation from Wilhelm Schickhardt:

"I say that all lines, even the straightest, which do not stand directe contra pupillam [directly in front of the eye] . . . necessarily appear somewhat bent. Nevertheless, no painter believes this; this is why they paint the straight sides of a building with straight lines, even though according to the true art of perspective this is incorrect . . ." (34).

and then, the delightful "conclusion" at which Schickhardt arrives, . . . "Crack that nut, you artists!"

come on. that's hysterical.