Masks & Overlay Blending

This was my first attempt at using the calculations tool to blend color channels to create a mask. I used the pen tool to include parts of the image that the mask didn't pick up. Then the overlay brush is used to finesse the selection. This is a very effective method for masking a tricky subject. The air guitar/tennis racket player was lifted from his original background and placed on this green field. I failed to address the shadows on his legs, however, creating an odd lighting discrepancy in the overall image.