This is the first of a two-part post on studio lighting. When I worked at Charles Cecil studios, a few of us were present at the opening of new studios and had to set up the lighting. It was a lot of work, but I came away with a good understanding of how to control light in a painting studio. (Apologies in advance for my photographic skills, but I hope to pick up a better low-light camera soon).

Charles Cecil's studio on Borgo San Frediano.
Most painters know that you need north light to avoid having direct sunlight moving around the room while you work (in the northern hemisphere only! I’ve heard of painters setting up north-lit studios in the southern hemisphere, only to have the studio blasted with sunlight). What they often don’t realize is how important it is to control the bounced light from outside as well.
One of the main errors I see in studio set-ups is not keeping reflected light off the ceiling. In a north-facing studio, anything you see from the window is facing south, and reflecting a lot of light. If you are blocking off the lower part of the window as most painters do, the light is still bouncing up onto the ceiling from the ground outside, and then coming down around the room. The best way to keep light off the ceiling is to put a hood over the top of the window. You can check the walls opposite the window to make sure the hood is keeping the reflected light out of the room. In my studio we just have a black tarp attached above the window with a wooden rod at the other end which is attached to a hook in the center of the ceiling.

Daniel Graves's studio in Piazza Donatello.
The lower half of the windows in most studios are covered to get a higher light source and also keep out colored light reflecting off buildings and trees. Generally speaking, the smaller and higher your light source is, the more half-tones you see. In the photo of Daniel Graves’s studio above, you can see how he has run a curtain perpendicular from the middle of the window in order to have different amounts of light on the model and his working space. The right side of the window has a high, small light source for the model. The left side is flooded with light so he can see what he is doing.

Ben Fenske in his studio in Piazza Donatello.
Ben Fenske paints some wonderful interiors with unusual lighting and in his studio he has light bouncing off the light walls, but still keeps light off the ceiling. In my Piazza Donatello studio (photo to be added soon) we have the walls covered with dark cloth to keep the subjects lit only from the window. In theory, if we ever needed reflected light, we could set up a light cloth on the other side of the subject. In practice, however, most traditional, naturally lit, paintings have only one light source. For portraiture especially, where working fast is of the essence, having a relatively simple pattern of light and shade makes everything much easier. Aesthetically, I also prefer the warm purple shadows you get with vermilion and black when painting a model lit with the cool light from a blue sky.
I was always taught about Rembrandt’s glazing and scumbling from warm to cool over the course of a portrait and how the different layers gave his sitters this wonderful pearlescent effect. Anyone who has ever painted a portrait under natural light will have noticed that over the course of the painting under changing light effects from the warm reflected light off clouds, to the cool light of the blue skies, chasing the effect naturally results in this layering of warm and cool layers in the paint. Just like so many old masters did before.