The Enigmatic Color of the Sun

Is yellow the true color of the sun? Our sun emits a broad spectrum of radiation, including visible light, which is crucial for life on Earth. In the vacuum of space, the sun appears white because it emits light across all wavelengths fairly evenly. However, when this light enters our atmosphere, it encounters air molecules and particles that scatter shorter wavelengths—primarily blue light—more effectively than longer wavelengths like red and yellow.

color of the sun

Simultaneous Color Contrast Explained…

Consider a small, clear disc placed against a blue background. The disc may appear slightly yellow due to the influence of the blue light surrounding it. This visual effect is similar to how we perceive the sun against the blue sky.In essence, while the sun itself emits white light, our atmosphere alters its appearance, leading us to see it as yellowish or orangish at times.

Additionally, not all species perceive colors in the same way. Different animals have varying sensitivities to wavelengths of light. This means their experience of color and light can be quite different from ours.

For more fun facts about color perception and optical illusions, visit Archimedes Lab.

Illusive Color Mixing

When your brain lies… There is NO yellow, nor red, nor green in the picture below! The only real colors are blue, cyan and magenta. Scientists and artists call these color induction effects “simultaneous color contrast” and “color assimilation”.

Concept taken from my book “Drawing Optical Illusions” (2010).
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When Optical Art Meets Illusion

Some simple geometric patterns and designs, when repeated, can induce strong illusory shape distortions. Thus, visual misperceptions are very common in the op art world.

If dark and clear rectangular tiles are arranged in a checkered fashion, as shown below, there is obviously no illusion, but wait, just add at the intersection of these tiles some transparent dark and clear square patches, et voilà, magic appears!

So, transparencies can produce apparent linear distortions. The parallel red lines in this example look like being convergent / divergent.

ZigZag, 2003
Available as prints and canvases from my online gallery
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Amazing Brightness Constancy Effect

Look carefully at the saw-tooth wave patterns on this picture. Is the background of the picture uniformly gray or are there different shades of gray?

Kolozanges (2013-2021), © Gianni A. Sarcone

Brightness constancy makes some vertical strips look darker, when in fact the gray background is all the same shade of gray.

This op art work is available as prints and canvases from my official online Gallery.

Turning Gray Shades Into Colors With A Tinted Geometric Grid

explanation

This is an old technique that uses the “color assimilation” effect to colorize pictures. This perceptual effect, also known by scientists as the Von Bezold spreading effect, occurs when our visual system transfers perceived colors to their adjacent areas.

Is the first photo of a variety of pumpkins in color?

colorized black and white pumpkins
Black and white photo overlaid with a geometrical tinted grid

Ghost Colors

This is one of my earliest color optical illusions. There is no yellow or green in the diamond shapes, just vertical black lines! (If you don’t believe it, use a eyedropper tool to check it.) This intriguing visual effect is mainly due to “simultaneous color contrast induction“.

Illusive colors
Ghost Squares / Black Diamonds (2002 – 2007)
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