Sketch Book for the Artist

OBJECTS

AND

INSTRUMENTS

Further Illusions

PSYCHOLOGISTS AND PHYSIOLOGISTS have studied optical

illusions for decades in pursuit of what they tell us about the

brain. Yet many illusions, including some shown here, are still

not agreeably understood. Artists make pictorial illusions

when they paint or draw, and we learn to read the styles of

diverse cultures and periods. Today we are bombarded with

images but rarely have difficulty reading them.

Some artists use known optical illusions to make art;

others adjust works to avoid their effects. Ancient Greek

architects knew parallel upright lines appeared to bend

toward each other in the middle, and so calculated

precisely how much to fatten columns to make them

appear straight. Michelangelo, among others, perfected

the acceleration of perspective (see pp.116-17) to make

painted figures look correct when viewed from below. In the

1960's, Op(tical) artists, such as Bridget Riley, made paintings

that depended upon the physical sensation of our brain's

reaction to known optical illusions.

SEEING TWO OPTIONS

Sometimes, when drawing the outline of a three-dimensional form, we will find that

in terms of the direction it faces, it oscillates between two possibilities. It is a curious

fact that we can never see both options at once; we can only look from one to the

other If an artist is not aware this can happen in their image, their picture could be

ambiguous. A few suggestive marks will tip the decision one way or the other

Closing the surface

When a transparent elliptical object has been

drawn, such as the dish seen here on the left,

it can oscillate between facing

toward or away from us, as

shown on the right. Closing

the surface of the form

seals our decision as to

which way it faces.

Two ways of seeing

This is the box created in the fourth

step on p.76. It is possible to read it

two ways: as a truncated rectangular

pyramid seen directly from above; or

as a sloping-sided rectangular tray

(both are illustrated far right)

"The brain is so eager to name a fragment we see that we need

only a suggestion to grasp the whole. Artists can communicate

much in few lines and the viewer will do the rest of the work."