As a supplementary post to the recent Bleeding Through portraits, I thought it might be interesting to share an example of the specific role flash played in the shoot.
The above image split of Bleeding Through's guitarist, Jona Weinhofen, shows two images shot a fraction of a second apart. On the left, the scene is lit entirely with ambient light, while flashes were triggered in the image on the right.
Daylight vs. Flash:
As you can see, the natural lighting was very high contrast, with deep, cool shadows with the sun acting as the key light. On the right, flash is acting as the key while the sun here creates the fill. Flashes behind to the subject provide a little more interest playing off the folds of the jacket and brighten up some details of the clothing.
Ambient was underexposed by about a stop in the above. The flashes were fired on manual at full-power and triggered wireless through Nikon's CLS system of IR triggering. You can reads about the full setup for the speedlights in the original post for the shoot.