Controlling contrast is difficult in bright sunlit exteriors. Exposing for either highlights or shadows will leave the other severely under-or over-exposed.
Tiffen was recognized with a Technical Achievement Award from the Academy of Motion Picture Arts & Sciences for the innovative design of this popular Motion Picture and TV filter.It uses the surrounding ambient light, not just light in the image area, to evenly lighten shadows throughout. Use it where contrast control is needed without any other effect on sharpness or highlight flare being apparent.