Land Effect
Safety Warnings
Warning: Projector Lamp Heat
Purpose
Two projectors overlay a black-and-white image with a red-filtered image of the same scene. Students perceive blues, greens, and other colors that are physically absent, demonstrating that color vision depends on luminance ratios across a scene rather than absolute wavelength content.
Figure 1:
Original color reference scene used to create the demonstration slides.
Figure 2:
Black-and-white slide, taken in white light. One of the two slides used in the dual-projector setup.
Figure 3:
Black-and-white slide taken through a red filter. This slide is projected through red cellophane and overlaid with the white-light B&W image to produce the Land Effect.
Figure 4:
Dual-projector setup. Red cellophane on a lens mount is placed in the beam of the red-filtered slide projector.
Equipment
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