People that make portraits of people using camera technology, especially modern high-resolution cameras, pay a great deal of attention to lighting their subject well and doing so artistically. They have to. Their camera, after all, is a recording device which takes a quite literal sample, in time, of the available light that is present in the scene. It is very difficult and painstakingly labour-intensive, even with photographic manipulation software, to go back and alter the light.
Photographers, instead, spend a great deal of time ensuring that the right light and shadows, of the desired colour and intensity and with the right softness in the transitions, is played on the model’s face, so that the image looks stunning in reality, with no further post processing necessary to the captured image. This is, by far, the most efficient way to make high quality photographic portraits. Beauty photographers, as far as I can tell, are the most meticulous about lighting faces sympathetically and artistically.
What I’ve noticed about portrait painters and those that paint from life, however, is that they pay far less attention to the lighting. Some might say they pay scant attention to lighting the subject in an artistically sound way and are almost haphazard in their approach to lighting. Perhaps portrait painters are missing a trick.
Of course, portrait photographers have to get the lighting right, because that is their finished look, whereas painters can adjust and compensate for bad lighting, on the canvas, with their tonal choices in paint, but you do have an easier time getting the facial feature definition, if you have lit the model well. There is no doubt that an artistically lit model can highlight features and facial shapes which are harder to see in bad lighting. In fact, bad lighting can mislead your eye into painting grotesque facial features and shadows, thereby losing the likeness. Using superior lighting to find better definition in the facial contours and features of the model probably makes it easier to get a good likeness, as a painter, regardless of how much you subsequently play with tonal values or substitute false colours for natural ones. It’s very hard to paint what you cannot see well.
To light a subject well, portrait photographers use a combination of diffusers, reflectors, key lights, fill lights, catch-lights, modifiers and gobos. They pay attention to lamp colour temperature and place the lights at specific distances from the subject to get desired effects. The angle of incidence of each light is used to define the features of the face, so each lamp needs to be placed precisely. They know that the intensity of a light source impinging on a surface, like the skin of the model’s face, drops away in inverse proportion to the square of the distance. There’s a lot to know, to use the gear well. Simply buying the right lights isn’t enough. Also, not buying any of the necessary gear makes lighting a model well extremely difficult.
I found some useful tutorial links that go into the methods photographers use to create good portrait lighting:
Setting up the lights that illuminate the subject and any reflectors and diffusers that modify the light in an artistically desirable way is important, if you want to paint highly realistic portraits. It even helps, just to ensure your draftsmanship is as accurate as necessary to capture the subject’s likeness.
The lights don’t have to be static, while you paint, either. It’s not like a snapshot. You can play with the lighting to bring out the definition of different facial contours, almost like mapping the three dimensional topography of the face. This may help, part way through painting the portrait, to more clearly define a facial feature or contour that you are struggling to interpret, always making sure you can restore the lights to their initial position, by taking measurements and making markings on the floor and photographic lamp stands, if required.
Don’t forget, however, that a subject sitting amongst a photographic lighting rig for any length of time will feel the discomfort of the heat and brilliance of the lamps, after not too long, so plan for breaks in the session, where the model can relax. Alternatively, turn off the more intense lights completely, from time to time, to reduce the discomfort to the sitter. There should also be cold drinking water, to hand, to rehydrate the model. You don’t want them fainting, due to dehydration or heat stroke. Painting an uncomfortable model results in a finished portrait that looks exactly like a rendering of somebody in great discomfort. Not a good look.
Like the best portrait photographers, don’t forget to create an interesting background or have some props in the scene, so that the painting’s background is interesting too. Posing a subject without any context encourages drafting errors, distortions in the bodily or facial proportions and mistakes in interpretation. The props and background can help to orient the subject in the scene and give reference points for measurements; useful when drafting the initial sketch of the subject.
The problem with lighting like a portrait photographer would is that there will, inevitably, be a lot of lighting gear in the way, which as a painter you will need to mentally “tune out” and remove from the scene you paint. This is where the ability to paint imaginatively actually comes into its own. You can simply paint the scene as if the lamps were not in the way. Cameras cannot do that. Removing the extraneous equipment captured in the scene in Photoshop is, again, quite painstaking and labour intensive, though it can be done.
In a life class situation, where artists usually position themselves around the model, the lighting will only be optimal for a very few positions, with the other artists compromised in their view of the model’s lighting and perhaps even dazzled by lamps facing toward them. There isn’t much you can do about this, other than use more diffuse light sources of lower intensity and ensure that the lighting works as well as possible from every vantage point and angle.
I think that lighting and composing the scene you wish to paint, with care, is an excellent starting point for any portrait painter. Haphazard lighting or context-free poses invite error, even for the most experienced of painters. Even if you can paint well, without caring too much about lighting and the scenic elements placed around the subject, taking the time to light the subject sensitively and adding some background interest will definitely produce better results. It simply removes some of the guesswork and frees the painter to ignore some real life elements visible in the scene, rather than have to synthesise them in his or her imagination, from nothing.
If you have the lighting equipment and props, it’s worth experimenting with, I think.