Watch closer. It is a wrinkle in his shirt that unfolds. When you wear a suit and tie, everything is smartly tucked and under a little tension here and there. Also, some of the shirts are rather stiff from a good pressing. So as you move about you can sometime even feel the fabric fold and become taunt and move as you move. That is what you are seeing. Watch the shadow in the fold even. That is all you are seeing.