I think about the sun when lighting the model because I know that everything we do in a painting inevitably references our natural environment. Even if we spend more and more time indoors under artificial lighting, the experience of the sun is a very powerful influence on our understanding of a figurative painting. We prefer our pictures to conform to our experience. Like sunlight, indoor lighting is very often above the figure, and when it is not, it looks strange. Even if the artist provides a context for artificial light below the figure—stage lighting at a theatre, for example—we still see a strangeness in it.
So let's think about where the sun is in the sky. When lighting the model, a good place to start is by positioning the lamp at a combination of 45° angles, halfway between the floor and ceiling and halfway between the fronts and sides of the model. This angle feels very comfortable because it relates to our experience of sunlight.
The sun casts light from two directions. Throughout the day in the Northern hemisphere, no matter what time it is, the sun casts light from the south toward the north. This is because the sun is not directly above us, especially in the winter. When we are facing south, the sun is before us. Facing north, it is a little behind us. But the sun also moves from east to west and this positions the sun from another orientation. So, while the sun shines from south to north, morning light is cast from East to West, and the opposite is true in the evening. This is why, when people say, "just look at the sun and you can figure out what direction you are facing," it's not always so simple.
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| 45 Degrees |
45 degrees is a good reference for two reasons. First, southern sunlight hits the northern hemisphere of Earth at an angle of 45° in the summer at noon when it is 90° above the Earth. Solar panels and south facing hills in vineyards are angled at 45° to collect sunlight. Now that it is winter, this angle has changed to around 36° at noon, but 45° is a good standard.
Secondly, in the morning and afternoon, the sun is hitting the Earth from another 45 degree orientation. When the sun moves from the East to the West, it casts light at a variety of angles to the East and West. A common angle of lighting for landscapes and architecture is the 45 degree cast shadow. This occurs in the morning after sunrise and in the evening before sundown, with the actual time depending on seasons, and this light produces warm light and cool shadows. Architecture photographers utilize this natural light when photographing the exterior of buildings. Midday light, around noon, tends to flatten out form because it doesn't give us longer, cooler shadows.
The clock face originates in the Northern European sundial, with noon right at the top. A simple way to envision the angles of light above the Earth is to think of squeezing the 12 hours of the clock into a semi-circle, like a sundial, instead of a full clock face, considering sunrise to be 6 a.m. and sunset to be 6 p.m. This is a rough approximation, but it will suffice. My sundial runs counterclockwise to put west on the left side. If this "sundial" were raised up perpendicular to the ground plane, you can see that positioning the lamp at 45° angles gives us 9 a.m. and 3 p.m.
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| Position of the sun above the Earth throughout the day |
In nature, the angle of the sun has a bearing on color temperature and so color temperature is one of the most important ways to render form in a painting. In the studio setting, the spotlight is always going to be about the same color no matter how you position it, so we have to carefully choose the color of our light and the color of architecture and clothing that reflects the spotlight. Sunlight, however, changes colors throughout the day giving us a range of warms and cools within the subject. Sunlight travels through more of the atmosphere when it is low on the horizon, scattering the blue light and streaming the red light. Except at dawn and dusk, you can look directly at the distant horizon and see all this blue light greying and bluing out the distant topography.
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| At 6 p.m., sunlight travels through more atmosphere |
I think of it like a cross-section of PVC pipe. When I'm cutting pipe, it's harder at first, and then when I get halfway through it gets really easy. But then it gets hard again. This is because, like the sun in the atmosphere, I'm going through a lot more material when cutting across rather than through the plastic. At midday, the light will appear cool and the shadows will become warm. At noon, the sun travels through the thinnest space of atmosphere. At midday, therefore, the blue light cuts right through the atmosphere and the lighting will appear cool and the shadows will become relatively warmer, as a result.
You can get spotlights with different color temperatures, and depending upon what you use to bounce the light, you can play with warms and cools in the highlights, shadows, and reflected lights. You can get some interesting effects using multiple light sources, as well. However you choose to light the model, though, sunlight will always set the standard for what we find natural.
