A major benefit to studying commercial photography is learning to take better portraits in different settings (outdoor or studio), using different equipment, and different lighting conditions (natural light vs. tungsten). Hard vs. soft light.
Each portrait was done in studio using different lighting conditions. Number 1 is soft light, number 2 (profile portrait) is using side lighting, number 3 is soft light again but in different ratios and a different background. In number 4 two lights were used (a hair light and key light).