Trigger Happy
230
size you would draw the snoozing cat on the garden
wall if you traced her outline on the window.
Now usually, any object B that subtends a larger
view angle than object A has a correspondingly larger
plane projection. This is common artistic sense: it looks
bigger, so you draw it bigger. But there are certain
cases where view angle and plane projection do not
tally. The simplest instance is a drawing of a sphere
that is to one side of our vision. It subtends a smaller
view angle than a sphere directly in front of us, but it
has a larger plane projection. According to true
perspective, therefore, it should have an elliptical, not a
circular, outline. This is how we see, but it would “look
wrong” to draw it thus. (Consider how odd a
photograph looks taken with a “fish-eye” lens, even
though it represents our field of vision more accurately
than standard equipment.) Renaissance painters already
knew that these sorts of compromises had to be made.
A book on the subject argued that “il ne faut pas
dessiner n’y peinder com[m]e l’oeil voit.”
35
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35 “One should not draw or paint exactly as the eye sees.” Bosse,
TraitÉ des
pratiques gÉometrales et perspectives
(1665).
