How contrast alters the apparent size of dark and bright bodies
Notes on derived shadow, luminous fields, and why buildings loom larger at night or in fog
A short block of notes on the perception of light and shade. Among equally dark objects seen at an equal, long distance, the one set higher above the ground looks darker, and the edges of a derived shadow are sharpest where its projection falls nearest the original shadow. A shadowy body ringed by a brighter field appears smaller, while a bright body bordering a darker field appears larger; hence buildings seem to lose height when lightning flashes behind them, yet loom larger in fog or night than when the air is clear and lit.
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Sharpness of a derived shadow
The edges of a derived shadow are more distinct the nearer its projection falls to the original shadow. The note pairs this with the observation that, among equally dark bodies at equal distance, the higher one appears darker.
Bright and dark fields change apparent size
A shadowy body surrounded by a more luminous field shows itself smaller, while a luminous body bordering a darker field shows itself larger. This is contrast affecting perceived magnitude.
Why buildings loom larger at night and in fog
The height of buildings seems to shrink the instant lightning flashes behind them, and the same buildings appear larger in fog or at night than when the air is clear and illuminated. The example applies the contrast rule to what a painter sees at a distance.