The Tiffen 5.65 x 5.65" Softnet Black 4 Filter is a softening filter meant to replicate the look of draping silk over the lens in order to soften or diffuse light. This filter works by scattering light entering the lens through a mesh pattern, resulting in an overall even, soft glow. The black distinction helps to maintain the overall contrast of the scene by reducing the overall spread of light into the shadows. The 4 density provides more softening than the 3.
Tiffen filters are made using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass and grinding flat to a tolerance of 1/10,000th of an inch. This filter measures 5.65 x 5.65" / 143.5 x 143.5mm.