Portraits are not perfect moments, they are staged with good lighting and flattering poses. Perfect moments are the candid shots that capture the true emotion and personality of the person. While there may not be perfect lighting you can always change that through photoshop or some other editing software.
There is no "perfect" moment that a photographer catches..... It is usually the unplanned/unposed portriats that make the "perfect" picture. The photographer just happens to be holding the camera at the time.