NHK Engineering System or NHK-ES have come up with a way to prevent water droplets or spray sticking to your lens. Working with other interested parties since 1997 NHK have produced a lens filter that disperses water from the glass surface.
Thread sizes for the NHK waterproof lens filter are 82/86mm, 105mm, 107mm, and 127mm.
Read the Japanese to English translation:
Jointly NHK, a light film, Ltd. Shonan Institute, NHK-ES, has developed a filter to prevent the adhesion of water droplets can be attached to the front surface of the lens. In the photo on the right compared to a normal filter, you can see that not a drop of water in when you spray the water, visibility is clear. “A drop of water to prevent filter” this is what conduct the study from 1997, improved the life and durability. Handling was also facilitated by employing a circular screw. Further, for use in the broadcasting camera, achieving a high transmittance of 90% and a flat in the visible light region the spectral transmission characteristics of the filter (wavelength vs transmittance).
Water droplets prevention filter is made of a two-layer structure as shown in the figure right, hydrophilic film of the first layer has a role in maintaining a flat surface by diffusing absorb the water droplets. With the help of ultraviolet light organic matter, such as oil, dirt, light catalyst layer of the second layer, has the function of decomposing into carbon dioxide and water, etc.. The combination of these two layers, we have maintained over a long period of time to prevent water droplets effect
To find out more about the waterproof lens filter and to order one please see NHK.