Profoto has produced a series of videos in which Joe McNally explains the benefits and applications of TTL, lighting ratios and high-speed sync.
The videos were made to promote the Profoto B1 and B2, two lights which offer wireless TTL for Nikon and Canon. Such features are not unique to these lights, however: you can use them with camera brands’ own shoe-mount flashes, third-party TTL triggers or competing TTL studio lights. Thus you don’t have to be an aspiring Profoto shooter to benefit from Joe McNally’s explanations.
The Profoto B2 TTL studio flash is $400 off in the USA until the end of September.