Value Study, back alley behind Dave Dornan's building in Helper

This is a value study done in a mix of ultramarine, yellow ochre, and alizarin crimson.  The idea behind this is to match your values as exactly as possible to what you are seeing.  Once you have done this, you can then color match over the top of the painting by matching your values and color.  If you have the underpainting like this exact, you have won half the battle and it makes painting the rest of the painting much easier to finish.