The Tiffen 6.6"x6.6" Ultra-Contrast Filter 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.
WARNING: This product may expose you to chemicals which are known to the State of California to cause cancer. For more information go to www.P65Warnings.ca.gov.