Distinctions of Seeing: Principles of Perspective

(Things We Don’t Know We Know)

To be read along with:

• “Perspective Drawing: Basic Principles” (Irma Ostroff)
• “Architectural Graphics” (Francis Ching), Chapter 6
• www.khulsey.com/perspective-2pt.html.

Perspective is not magic. It can be learned by following a set of instructions. But it is basically consistent with how we naturally see, a human function that we have taken for granted (have no distinctions around) and are generally unconscious to. The following points are basically invariant principles or laws, like in physics, of how we see.

• What you see is determined by where you’re looking from (Station Point). There are an infinite number of station points (around, above, below, closer, farther). If you move your station point, you change your view.

• You see most clearly within about a 60 degree Cone of Vision. Outside of that is peripheral vision.

• The apparent size of things diminishes with distance.

• Lines not parallel to the Picture Plane (where the image is cast) are progressively shorter (Foreshortening) the more perpendicular they are to the Picture Plane.

• Parallel lines converge towards Vanishing Points.

• Hidden Lines exist, but are not visible from the Station Point.

• The size of the image is determined by the position (relative to you at the station point) of the Picture Plane, like a movie screen.

• There is always an (imaginary or real) Height Line, like a surveyor’s measuring rod.

• We see surfaces and tones or color, not lines, but, fundamentally, perspectives are constructed from lines.

• The image is actually re-constructed in your brain as a two-dimensional

Projection, like a slide in a projector.