The Formatt Hitech 77mm -20 UV Filter is an underwater filter that is designed to absorb ultraviolet light and improve color accuracy at depths of 59'.0 to 65.6'.





Due to its density, water naturally attenuates radiation, including visible light. Lower-energy wavelengths of visible light that are apparent as red, orange, and yellow colors are attenuated more than higher-energy wavelengths of visible light that are apparent as blue, indigo, and violet colors. This further obscures the ability to see red to yellow hues, and can otherwise limit underwater life or objects to appearing only in shades of blue to violet.





Additionally, particles suspended underwater can reflect and scatter ambient sunlight. When this occurs, higher-energy wavelengths within sunlight such as ultraviolet light and visible light that are apparent as violet and blue colors are more easily reflected than lower-energy wavelengths of visible light that are apparent as yellow, orange, and red colors. Together, these particles, along with the ultraviolet, violet, and blue light they are reflecting can obscure details within a scene while further imparting an unwanted bluish cast.





The Formatt Hitech 77mm -20 UV Filter can help improve the results of underwater images at depths of 59'.0 to 65.6' by effectively absorbing ultraviolet light and reducing visible light that appears as blue and violet. Available red, orange, and yellow light is allowed into an underwater housing and camera, helping to improve color balance throughout the frame.





This filter is constructed from Schott B270 glass for increased optical clarity as well as color fidelity and features an aluminum-alloy filter ring for durability while remaining lightweight. When used, the Formatt Hitech 77mm -20 UV Filter's 0.1 density darkens the entire image by 0.3 stops. This reduction in exposure can be compensated for by adjusting the aperture setting of the lens it is placed on, or the shutter speed of the camera being used.