Selected Bibliography Architectural Graphics | Seite 132

TONAL VALUES
Vision results from the stimulation of nerve cells in the
retina of the eye, signaling patterns of light intensity and
color. Our visual system processes these patterns of light
and dark. and is able to extract specificfeatures of our
environment-edges. contours. size. movement, and color.
If seeing patterns of light and dark is essential to our
perception of objects. then establishing contrasts in value
discernible to the eye is the key to the graphic definition of
light. form, and space.
Through the interplay of tonal values we are able to:
• Describe how light reveals t he form of objects.

• Clarify the arrangements of forms in space.

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• Depict the color and texture of surfaces.

126 /ARCHITECTURAL GRAPHICS