This is the 2007 version. Click here for the 2017 chapter 04 table of contents.

Depth Cues Pt 2

Linear perspective—the tendency of parallel lines to converge in the distance—is a depth cue employed by artists since the Middle Ages. Students are taught in art classes to draw lines to a point on the horizon, as a guide for drawing in perspective. This conveys an accurate impression of depth on the 2-dimensional surface of the canvas. Photographs can show vivid linear perspective, as in this example.

What is the depth cue of linear perspective?

Linear perspective as a depth cue

The road leads to a point on the horizon, creating an impression of depth that influences our interpretation of other parts of the picture. Notice how the human figure, which looks normal at a distance, appears tiny when copied to the near side of the road. This effect occurs because linear perspective determines our judgment of distance, and that shapes our perception of size.

What was Helmholtz's concept of "unconscious inference"

When the brain makes an automatic assumption, based on information coming into the senses, this is called unconscious inference Helmholtz described unconscious inference in the 1800s. We infer (logically deduce) the physical size of the figures, depending on what we "know" about their distance from us. We make this inference automatically and unconsciously.

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