An Artist’s Guide to Sunrise & Sunset

This month’s Landscape Art Club theme is Sunsets, which works for me: I love sunsets! Painted by Natalia has a great feature this month on sunset technique with lots of reference photos, and looking through them got me thinking about the science of sunsets – and for that matter, sunrises! Why are they the way they are? And can that knowledge help to paint them better? I had fun learning about the moon for my Artist’s Guide to the Moon, so I thought I’d put together some info on sunsets.

A caution about working from (my) sunset/sunrise photos

I’ve included a lot of my own photos below where I could. Skilled photographers/photo editors can create great sunset photos, but I am… not that, really. I find that the ones I take have some consistent problems that I can inadvertently replicate in my paintings when I use them as references:

• Lights are too light/blown out while darks are too dark.
• Cloud colors are consistently too orange and not pink enough.

Sunset Science Questions

Why does the sky turn red at sunrise and sunset?

When the sun is closer to the horizon, the available light is slanted at an angle, and travels through more atmosphere to get to your eyes.

The atmosphere scatters the light (this is called Rayleigh scattering). This tends to remove short-wave colors like blue and violet and leave long-wave colors like red and orange.

What order do the colors go in?

On a clear sky when the sun is low, toward the horizon:

• Colors are more vivid toward the horizon and closer to the sun (so, the side of the sky the sun is on).
• Colors get redder toward the horizon (except maybe for a golden halo around the sun itself).
• The sky color will tend to be blue toward the zenith, then yellow or white, then orange to red.

How does the sky grade from blue to yellow without going green?

When you mix paint, blue + yellow = green. So when you lay blue and yellow next to each other to paint a sunset, it’s a common problem to get too much green. So why don’t we see that green in the sky?

Light mixing works differently. When you mix green and red light, you get yellow.

Green light is scattered weakly by Rayleigh scattering. Green light in the atmosphere will tend to look yellow (if it’s closer to the red horizon) or turquoise (if it’s closer to the blue zenith).

A tip I was taught for sunsets is to stick some red between blue and yellow, to avoid the painting going green. Unfortunately, that’s not really the order in which colors go in the sky (as above). You can always stick a cloud in there to mess things up, though.

While you do have to take care in painting sunsets to use colors that don’t tend to go green easily, I do think we can be too dogmatic about as artists sometimes. The sky does kind of go green-ish in some sunsets, though it often has an interesting quality of looking yellow + turquoise at the same time.

The best trick I have found to avoid sunsets going too green is to use yellow colors that don’t easily turn green, such as Naples Yellow Deep (PBr24), or some form of yellow ochre, gold ochre, or raw sienna (usually PBr7 or PY42 or PY43). Avoid PY150 or Quin Gold, which mix green very readily.

What factors contribute to a great sunrise or sunset?

Clouds

I’ve found that the most glorious skyscapes involve clouds. While a clear sky will show a clean gradient (as above), clouds can add all kinds of interesting shapes and bursts of color. Clouds reflect the light below them, so when the sun is low in the sky, the clouds above can reflect bursts of pink or red color that contrast with the blue or gray backdrop in the upper part of the sky.

The reflected colors on the clouds can be even bolder and more intense than background sky colors, and the shapes of clouds can introduce all sorts of interesting shadows.

Of course, you need the right amount of clouds. Too much thick cloud cover may relegate the light show to a small area, or block it entirely.

Clean Air

Smog and pollution can block a lot of the vivid colors of sunset. City sunrises and sunsets can have a tendency toward brownishness, especially on days with poor air quality.

Dry Air

Water vapor in the air can absorb some of the light, so sky colors can appear relatively washed-out on humid days.

When I lived in the Boston area, I found that sunrises and sunsets were more vivid in winter, when the air was colder and dryer, compared to muggy, hazy summer. The climate in Vancouver is different, with relatively dry summers and wet, rainy winters, so summer’s a better sunset season here.

This is also why deserts have such great sunrises and sunsets!

What’s the difference between sunrise and sunset?

There are the obvious definitional differences:

• The sun rises in the morning and sets in the evening.
• The sun rises in the east and sets in the west. (So an image of glorious colors over the ocean is more likely to represent sunrise in Cape Cod or sunset in Los Angeles.)

But visually, if you’re looking at a photo, and you don’t know the time or location/direction it was taken, can you tell the difference between sunrise and sunset?

According to Live Science, the phenomena are the same, just in reverse. But some people may perceive sunrises as being more intense because the eyes are rested and adjusted to the dark, while others may perceive sunsets as being more intense if they live in a smoggy area where particles in the air diffuse light more in the evening.

Here’s another clue I’ve noticed: Sunrise images are more likely to contain fog and mist. Fog is more likely to form in the morning because that’s the coolest time of day; fog needs cool air temperatures and high humidity. In daytime, the air and ground temperatures are often too warm for fog to form. Of course, not every sunrise has fog (you won’t get fog in a dry climate or season), and evening fog is possible in the right conditions, but most of the time I have found that fog is a morning cue.

Conclusion

I often find that learning some science facts helps me to make my paintings more convincing. Learning what is possible or impossible, or more or less likely under certain circumstances, can help me to convey the feeling I want to, and situate my viewer more firmly in a sense of place. Some things I will take from this exploration:

• Putting sunrise/sunset sky colors in the right order: blue, yellow, red
• Adding vivid pink clouds for interest
• Using mist to convey a sense of morning
• Using vivid or pastel sunsets to imply dry or humid atmospheres

I hope this has helped you, too!