Equiluminance.

The brilliant gold stars in Van Gogh's Starry Night fade into the background when the painting is seen in black and white. The yellow of the stars' center is equiluminant to the white/beige glow they create in the colored picture. The range of different blues used in the sky and the various white, blue, and gray colors used in the swirling parts of the sky are equiluminant, too, and become one shade of gray when the color is taken away. The hills, which have layers of blue and gray in the original picture, take on a consistent gray color as well in the black and white version of Starry Night.

Van Gogh painted the outlines of forms in his painting with black, so the objects can be seen clearly in both versions of the picture. However, the various beautiful colors that give the objects their rich texture fade into each other in black and white, as if Van Gogh had filled in all of the outlines with single colors.