Why would any rational person choose portrait painting as a career? Before photography, painting was the best way to capture an image. Now, with modern technology that can capture an image in seconds, why spend years learning how to manipulate a centuries-old medium? Furthermore, what rational person would commission a portrait painted of themselves and choose to sit idle and most likely uncomfortable and most definitely bored, for hours to end up with nothing but an image to hang on a wall and gather dust?
Portrait painting is a unique art, one that requires an extraordinary amount of time and dedication to master, and sitting for a portrait can be physically and mentally exhausting for a model. It would seem that modern photography has rendered the ancient art obsolete, but this is far from the truth. Photography can't replace painting (and vice versa) because the two mediums produce such different results. However, a good portrait painting is technically superior to a photograph, and a great portrait painting is more challenging to an artist and meaningful to a patron.
There are many reasons why painting, specifically oil painting, is technically superior to photography. Visual effects can be obtained by complex layering of paint that cannot be created by the layer of ink on a photograph. A basic example would be the technique of glazing, the layering of transparent oil containing translucent particles of pigment spread over a white ground. The colors produced can be nearly as luminous and bright as sunlight through stained glass and as subtle as skin tone or embroidered velvet. The brilliance of skin in a Rembrandt painting could not be represented by ink on paper. (In fact, it is impossible to accurately photograph a Rembrandt painting. Photography does not have the necessary range of expression to capture the full effect of light falling on his paintings.) Another more subtle example of oil painting’s technical superiority would be the freedom of the artist to interpret the image. Michelangelo's figures in the Sistine Chapel could never have been photographed for a simple reason-- they could never have lived. The anatomical proportions of his figures are physically impossible. His conscious, incredibly graceful distortion of the human form succeeds in crafting powerful, intensely alive figures, a power that could not be tapped in photography.
It would seem that the most obvious difference between photography and oil painting would be necessary commitment of time. A photograph can be done in seconds, and then printed in a few hours. An oil painting can take hours of sitting for the model, and weeks if not months or years of work for the artist. Leonardo da Vinci's "Mona Lisa" was painted over a period of six years. This time commitment can be an obvious inconvenience for a model. However, the necessary time commitment of an oil painting is a necessary part of good portraiture. A woman's appearance, her physiognomy, is not simply determined by the way light reflects off the surface of her skin. It is conveyed in her facial expressions, in the way she holds her head, focuses her eyes, and in her posture. Unless a photographer is extremely familiar with the model, and unless the model is unusually good at sitting naturally and maintaining the unconscious tension of facial features that express a specific mood, the picture can be nothing but a snap-shot. It can only capture a temporary flash of expression that rarely captures anything deeper than a momentary thought or emotion.
A painter, on the other hand, has the opportunity to watch the model's expression change, to watch how she holds her head when she's tired, or excited, or melancholy, or content. The artist can incorporate these observations into the painting, expressing not only what the model looks like, but also how she looks. I painted a portrait of my father recently, and he commented that it's the only image he's ever seen that looks like him. A good portrait painter has the ability to perceive and then convey the truth of a person's appearance; through this accurate depiction of appearance, a painting can simultaneously convey the truth about a person’s character. Such painting can be an act of recognition, it can be an artist saying, "This is reality. This is fact.This is how you look to me, and who you are to me." But a good portrait is not great art.
Great art, like all greatness, is a challenge to those who encounter it. A great portrait painter would say, "this is what you could and should be. This is how beautiful you can be, how thoughtful, how alive." Looking at a great portrait is not like looking at a mirror for the model, it's like looking at a reflection of the model's best possible self. To the man with high self worth, the portrait will be praise, a commendation every time he looks at it, but to the man of low self-esteem, it will be an unbearable reminder of his squandered potential. This powerful message is the ultimate goal of a great portrait painter. To the subject of the portrait, such an image is priceless.
Perhaps this is the meaning of Rainer Maria Rilke's poem, "Archaic Torso of Apollo." The poet writes of the stunning beauty of an ancient sculpture, and ends, "for here there is no place that does not see you. You must change your life."