TIFFEN IRND 4×5.65 SET

Tiffen Full Spectrum IRND is a set of filters that cut the light reaching the sensor. They let you keep the aperture open on a sunny day for a soft background, and hold a 1/50 shutter. The "IR" part matters: plain dense NDs pass infrared to a digital sensor, so black clothing turns deep red and black hair goes brown. IRND blocks that light, so colour stays true even at the heaviest densities. The set covers 0.3 to 2.1 (1 to 7 stops).