When recently photographing a child, I shot the necessary posed shots. After a few setting changes, I let him walk around and I followed with the camera.
He started looking out the window to see who was coming. With just the natural light I captured this shot. I performed some post work and rendered a great candid portrait. Window light is important. Especially for the amateur photographer without a lot of money in the budget for expensive lighting. Even the big wedding photographers use this technique as it provides great soft indirect lighting on the face. The low saturation (except for the red sweater) and the timeless outfit give this portrait a very classic look.
Post work: decrease saturation - but INCREASED saturation in sweater. increased the contract, burned the edges/corners.