Scrim
A translucent panel placed in front of a light to reduce and soften it without changing its position.
Measured in
stops
In depth
A scrim is effectively a modifier that can be positioned independently of the light, which is what makes it useful outdoors: a large silk held between the sun and a subject converts hard midday light into a soft source the size of the fabric. Densities are quoted in stops, typically a half, one or two.
Examples in practice
A 2 m silk held above a subject turns overhead noon sun into soft, even light suitable for a portrait.