Shots were taken today using my recently-acquired (2 weeks ago or so) Vivitar 5600 hot-shoe flash. Used in bounce-flash mode, approximately 2 2/3 f-stop compensation (using discrepancy between f-stop selected on-flash vs f-stop selected on-camera, and setting ISO 100 on-flash vs ISO 400 on-camera). That would explain the "smoother" lighting, it really made a difference--far better than using the built-in pop-up flash.