John Singer Sargent.

An American Master. They say copying the old masters work is a good way to learn. I did learn a lot painting Sargent's, An Out-of-doors Study. He defines his shapes by using the strongest lights and dark tones next to each other: if you remove them, the whole painting is mainly a medium gray tone. This was more daunting to think about painting than it was to paint. A good study indeed.