This No.21 Orange filter with 46% transmission helps to reduce blue-green wavelengths. Sharpens the boundaries along the plains of Mars due to the reduction of blue/green transmissions. Use on Jupiter and Saturn to enhance detail in the belts and polar regions.
In use the moon is easier to observe and does a good job of eliminating the street light smog from below our apartment in the city. It also helps to see the shadows in the craters and give improved definition of the surface of the Moon.
This gradual filter is compatible with Cokin P series. Gradual filter is a MUST for digital users, because the digital sensor unlike film has very low exposure tolerance. Detail will be lost on both low and high light area. To correct this, you need gradual filter to balance it!