I was recently asked about why I prefer to work from black and white photos, rather than color, and wanted to share some of my thoughts on the reasoning behind it.
As I am painting, I am more concerned about getting the correct value relationships (how one value appears when placed next to another value) rather than a particular color. The reason is simple: Value sets the stage on which color performs. If the value is not correct, then the color will not be correct. Color has a tendency to fool the eye (which the Impressionists recognized and used to their advantage) and is sometimes difficult to judge in terms of value.
This effect can be seen in the examples below, especially in the pink areas in the background and the warm and cool color changes that take place within the dress. In the color photo there is an illusion of more values in the painting, especially in the background, but when you look at the black and white photo you will notice that the value relationships seem much closer (not as much of a jump from a lighter value to a darker value). Many of the changes that actually occur within the painting are the result of changes in color, not value. Working from black and white photos allows me to focus on the value relationships, which are crucial in order to achieve a three dimensional look that is full of atmosphere and depth. Once I have decided on the value that I need to work in, I can then adjust the color temperature to be either warmer or cooler. An understanding of value is extremely important in order to maximize the effects of color.
Monet was a great example of how value and color work together. He was able to paint an entire landscape by using only a few values, but was able to achieve a sense of volume within those few values by simply changing the color. He understood the importance of first getting the values right and then adjusting the colors within those values.
I typically work from three different black and white photos: one over exposure, one under exposure and one in between the two. I base my overall value relationships on the middle exposure but use the other two in order to get more information about the drawing within the extremely light and dark areas that can’t be seen in the middle exposure. By working this way, I am able to incorporate my own color, knowing that the value relationships are correct.
Having said all of that, remember that Value and Color must work together in order to be correct and that Value sets the stage on which Color performs.