Fill light / bounce
A weaker light or reflector that lifts the key light's shadows without taking over the direction of the picture.
See it
What it is
Fill light opens the shadows made by the key without becoming a new direction of its own. It can come from a second lamp, but often it is just the key reflected back by white foam board, a 5-in-1 collapsible reflector, a wall, or the ceiling. More fill lowers contrast; less fill lets the shadow side stay dense.
Reach for it when faces, dark fabric, or product labels disappear on the side away from the key. A white bounce gives broad neutral fill, silver returns more light with more bite, and unbleached muslin returns a warmer tone. If the shadows need to go darker instead, black cloth or foam board is negative fill, subtracting stray light rather than adding any.
Gotcha: fill is not supposed to announce a second sun. Put a bare fill too close to the lens axis and it can make a second set of shadows, flatten skin, and put an extra catchlight in each eye. Start with the bounce farther away than feels necessary, then bring it in until the dark side holds detail without matching the key side.
Ask AI for it
Keep the existing soft key, then use the bounce lighting technique with a 4 by 8 foot white foamcore V-flat just outside frame on the shadow side. Return enough key light to lift that side by roughly two stops while keeping it visibly darker than the lit side. Preserve one directional nose shadow and one natural catchlight per eye, with no second hard shadow and no flat frontal flash look.