underexpose

verb (used with object), un·der·ex·posed, un·der·ex·pos·ing.

1. to expose either to insufficient light or to sufficient light for too short a period, as in photography.

verb (tr)

1. photog to expose (a film, plate, or paper) for too short a period or with insufficient light so as not to produce the required effect
2. (often passive) to fail to subject to appropriate or expected publicity