Opening up your edges
When a very bright light source hits an object, our eyes perceive edges in a different way than a dimmer light source. The midtone colour becomes more saturated, and the highlight grows brighter as the light ricochets off the surface. To achieve this, use a soft brush and the midtone colour, at about 30 per cent Opacity, with the brush in Lighten mode. Run the brush along the highlight to open the edge.