optics Archives | Carol L. Douglas

February 28, 2022

Monday Morning Art School: the color of darkness

Painters spend lots of time thinking about the subtractive color system. We spend very little time thinking about the additive system. That’s a mistake, because this is the color of light.

A deer I painted years ago as a demonstration for my class. Shadows are the complement of the morning light.

Every artist is familiar with the three primary colors: red, blue and yellow, and their complements, the secondary colors green, orange and violet. This is the fundamental color wheel for the subtractive color system, or what’s used for paint and ink.

There’s another set that became more important in the 20^thcentury, with the rise of electric lights and then electronics. These are the so-called additive color primaries, which are red, green and blue. This color system doesn’t have a color wheel, but it does have complements, which are shown below.

Additive complements (left) and subtractive complements (right). Courtesy Wikipedia.

Painters spend lots of time thinking about the subtractive color system. We spend very little time thinking about the additive system. That’s a mistake, because this is the color of light.

For painters, color theory is a balance between natural light (additive color) and their paints (subtractive color). That’s mind-blowing but they’re not alone in this challenge. Despite working in an additive-color medium, many web designers still think in terms of subtractive color. This system has influenced our aesthetics since the 18^th century, and we don’t let go of what ‘looks right’ easily.

But in practical terms, shadows are the absence of light. If light is full-spectrum, then its shadows will be full-spectrum too. That means a white light will cast a grey shadow.

However, natural light is far more complex than that. It seldom shows up with all wavelengths being equal.

Sunrise, or the so-called ‘golden hour’ on Beech Hill. The shadows are definitely blue.

For this reason, artists have a useful rule: shadows are the complement of the color of the light. In the north on a snowy morning, golden light casts blue-violet shadows on the snow. In overcast light, the shadows are vaguer and full-spectrum, meaning they appear greyer. That’s easy to see, and demonstrates an idea that you can then generalize to all subjects. Although you should never trust your camera for color, I have included two photographs that show this.

Midday at the same location, the light is diffuse and so are the shadows.

It’s a mistake to get too attached to theory, however. For one thing, light is tricky. And for another thing, ‘primary color’ is another one of those constructs that we use because it’s useful, not because it’s absolute or provable. Our understanding and technologies are imperfect. CRT televisions of the 20^th century were dull compared to modern LED screens. As technology got better, so did the color gamut, and what was considered ‘primary’ changed accordingly.

Most importantly, all these color systems are a dim mirror of the interaction of natural light and the human brain. Both are complex and imperfectly understood.

Light and shadows exist in the additive system, so your understanding of primaries is wrong if it’s based on what you learned in kindergarten. The complement of yellow in subtractive color is violet. The complement of yellow in additive color is blue. So, if the light is golden, the complement is more likely to be blue than violet.

At sunset, shadows appear black. There’s color in those darks, but our eyes can’t process it.

On the other hand, at sunset, the light is often red. The complement of red in additive color is cyan, but we almost never see any colors in the shadows at sunset. Instead, they’re just black, because we’ve hit the limit of what our poor rods and cones can process.

There’s a lot of latitude in what colors you can make your shadows, as long as you maintain the warm-cool balance. And—as always—all the theory in the world is no substitute for observation.

January 31, 2022

Monday Morning Art School: the color of light

In winter, we’re in warm light from sunup to sunset, because the sun never really climbs very high in the sky. That’s our payoff for putting up with this weather.

Three photos of the golden hour, courtesy of Jennifer Johnson

The golden hour is that period after dawn and before sunset when the light is warm and the shadows are long and blue. The farther north you go, the longer the golden hour lasts. In winter in the northern United States, we’re in warm light from sunup to sunset, because the sun never really climbs very high in the sky. That’s our payoff for putting up with this weather.

Most of us prefer to paint that winter light from the comfort of our studio, but cameras lie. That’s the same black glove, below; the image on the left is with a cellphone camera and the one on the right is with a DSLR. In attempting to correct exposure, the cellphone is interpreting that black as purple.

Two photos of a black glove, courtesy Dwight Perot

So too does your eye-brain connection see things interpretively. You may see the same blue shadows in the three photographs at top, but I’ve sampled them and they’re not the same at all. In fact, they’re not even blue, but rather three variations of a soft blueish-grey. Your mind is interpolating what it knows to be true, which is that those shadows are cool. In this case it’s better to trust your mind than the hard ‘facts’ of camera and laptop.

Looking for Shellfish, Joaquín Sorolla, 1905. A warm light comes from our side of the figure, but there are warm shadows—the result of local color reflection from the rock. Likewise the bottom half of the torso reflects strong cool tones from the water and anchors the boy into the sea.

What we call light is really the narrow band of electromagnetic waves that our retinas can perceive. This narrow band is comprised of the colors of the rainbow, or what we sometimes call ROY G BIV. (There really isn’t an indigo; it’s there so that Roy has a pronounceable surname.) Each of Roy’s color names corresponds to a specific wavelength. For example, blue is about 475 nm; red is about 650 nm.

When the whole visible light spectrum strikes your eye at the same time, you perceive white. This is not a color in itself, but the admixture of a bunch of colors. In the real world, this is never a pure mix. The atmosphere bends light just like a prism does, so what you see is always tinted. The light might be gold and peach at sunset and cool at midday. Impurities in the atmosphere also give us the energetic indigo-violet of the far distant hills.

Valencian Fishwives, Joaquín Sorolla, 1903. Here the light is cool and the shadows are warmer.

The farther away something is, the more likely dust has filtered out the longer wavelengths, i.e., the warm colors. That’s why your plein airpainting teacher keeps telling you that the reds drop out first, then the yellows, leaving you with blue.

Just as all the colors together form white light, the absence of light is total blackness. But unless you’re in a cave or darkroom, that’s a theoretical construct. There’s always reflected light bouncing around in the shadows, and that light gives the shadows its color. It’s never black and it’s unlikely to be grey, either.

Return from Fishing, Joaquín Sorolla, 1894. The light is warm, the shadows are cool, and the places where the light is going through the sails are warmer still, since they’re filtered by the off-white fabric.

If the color of the light is warm, the color of the shadows is almost always going to be cool, and vice-versa. Knowing this and identifying the color of the light and shadow is the first step to a good landscape painting.

The exception to this is an object in filtered light. Its shadows and lighter passages will be variations of the same color temperature. This is how we instinctively know that something we’re seeing is under an awning, for example.

Catalonia: the Tuna Catch, from Visions of Spain, Joaquín Sorolla, 1919. In this case, most of the painting is in shadow, and what light there is, is filtered through the yellow awning. It is the distortion of the light-dark color scheme that tells us viewers that we are in an enclosed space.

Study the Spanish painter Joaquín Sorolla to understand the color of light. He was a master at painting white fabric in a variety of circumstances, and comparing the light passages to the shadow passages will tell you much about managing the color of light in your painting.

July 3, 2018

Mad dogs and Englishmen go out in the midday sun

How to paint in direct sun without your painting getting too dark.

Painting in the direct sun at Fort Williams. Not only did I need gallons of water, but I have the most ridiculous tan. (Photo courtesy of Karen Lybrand)

Yesterday, Cat Popesaw the above photo and asked me, “How do you work in the sun and not make your values too dark to compensate?” This is a common-enough problem. Experience has taught me how to compensate, but I used to do it too.

Yes, I could have chosen a shaded location from which to paint, but not at the edge of a cliff looking down into the water. I wanted that view and was willing to broil to catch it.

I have an excellent field umbrella: the EasyL by Artwork Essentials. However, the onshore wind in Maine often sends it flying. It’s gotten to the point where I don’t even bother. I wouldn’t have used an umbrella in the above situation anyway, because my canvas was already the size of a kite.

Painting with Brad Marshall along Long Island Sound, where the sea breezes are light enough to permit an umbrella. (Photo courtesy of Rye Art Center)

I started this painting with the early morning light hitting from the side. By the time the light was overhead, I had the value structure laid out. That’s important because a raking side light isn’t as strong as direct overhead light.

My red canvas is part of the solution. I aim for a value-neutral, high-chroma color. Not only is a very light canvas a liar when it comes to value, it causes eye strain.

Painting on a pale or white canvas makes you lay down those first strokes too dark. To understand why, we need to go back to the master of color mixing, Josef Albers. Albers understood that the same optics rules that played tricks in color also did so in monochrome. He did many greyscale exercises along with his more famous color work.

We perceive the dark square differently in a field of red than in a field of white.

To apply his insights to field painting in bright light, a dark square in an expanse of white reads differently than the same square in a field of mid-value color. That’s why white space is such an important concept in graphic design. In painting, we subconsciously use that white space as part of our design, and when it goes away, we’re left with something that’s dark and drab. It’s worse when the white board is shimmering in the sun. Our pupils contract terribly, altering our perception of color and light.

I mix my colors before I start painting. I have the darkest dark and lightest light set out before I put a stroke on the canvas. This limits my value range and defines my color temperature intellectually, rather than intuitively. I block in my large shapes, shooting for an average hue and value for each large mass. Then I stand back and look at the painting critically, to see if the composition laces together. If it doesn’t, back to the proverbial drawing board.

Historic Fort George, by Carol L. Douglas. This was painted without an umbrella, because I didn’t want to hike the Fort Point Trail carrying extra gear.

It helps to paint in the sky last. The tendency is to paint the sky too dark. This pulls the light level of the whole painting down to match.

I complicate matters by painting in my sunglasses. This isn’t a problem as long as I remove them and check my painting from time to time. The polarizing lenses cut the glare from both the water and the paint, so it’s not really that difficult to match colors accurately. And if the sea is a little bluer than in life, is that really so bad?