Hoya 72 mm HMC NDx4 Screw in Filter

Amazon Marketplace

For Wider Apertures or Longer Exposures enable slow shutter speeds decrease depth of field by allowing wider apertures reduce the amount of light reaching the film/sensor no affect on color balance

Amazon

Eliminates overly bright, washed-out images. Balances exposures. Increases control of depth of field. Equally effective in color or black and white photography. Multi Coated for flare prevention.