True Yellow

Humans distinguish blue, green, yellow, and red as unique hues. Unique hues are psychologically primary — we perceive them as pure rather then a blend of colors.

In higher and lower latitudes, seasons are associated with a dominant color palette: greens during the growing season; reds, yellows, and oranges during harvest; and shades of gray when the snow flies.

Olive Trees with yellow sky and sun
by Vincent van Gogh
Saint-Rémy, November 1889

The Minneapolis Institute of Arts

Seasons also seem to affect our perception of color. Psychologists at the University of York have published research indicating humans see yellow differently in the January (winter in the UK), than in June (summer in the UK).

"In York you typically have grey, dull winters and then in summer you have greenery everywhere. Our vision compensates for those changes and that, surprisingly, changes what we think ‘yellow’ looks like."
— Lauren Welbourne, University of York, Department of Psychology

Yellow is unusual among the unique hues because most people, despite differences in retinal physiology, age, and culture, tend to agree on true or unique yellow. Subjects in the UK exposed to chromatically adjusted artificial light were asked when the light reached true yellow. Significant differences in the recognition of true yellow occurred depending on whether it was winter or summer.

"What we are finding is that between seasons our vision adapts to changes in environment."
— Lauren Welbourne

Painters have long appreciated the changes in the quality of light over the course of a day or across seasons. It seems our minds adjust our perception of color to re-balance or compensate for some of those variations.

Some painters transform the sun into a yellow spot, others transform a yellow spot into the sun.
— Pablo Picasso

REFERENCES

• Changing seasons also change how you see color, Laine Bergeson, Discovery News, 5 August 2015.
• Human colour perception changes between seasons, Lauren E. Welbourne, Antony B. Morland, Alex R. Wade, Current Biology, Volume 25, Issue 15, pR646–R647, 3 August 2015.

Shafts of Sunlight

Shafts of sunlight, sometimes mythologized as God rays, Ropes of Maui, Jacob's Ladder, or Fingers of God, are atmospheric optics known as crepuscular rays.

Crepuscular rays are shafts of sunlight that stream through gaps in atmospheric clouds.

The shafts appear to radiate from a point in the sky, but are are nearly parallel. The convergence to a point in the sky observed on the ground, is actually a perspective effect analogous to how parallel train rails appear to converge at a distance.

“When you come right down to it all you have is yourself. The sun is a thousand rays in your belly. All the rest is nothing.”
― Pablo Picasso (1881-1973)

Crepuscular is derived from the Latin word crepusculum meaning twilight. Crepuscular rays frequently appear during the high contrast twilight hours of dawn or dusk.

“The human understanding is like a false mirror, which, receiving rays irregularly, distorts and discolors the nature of things by mingling its own nature with it”
― Francis Bacon (1561-1626)

REFERENCES

• Crepuscular rays, Wikipedia.