Fuction:
Reduces the amount of light reaching the film without affecting the color.
Applies slow shutter speed under strong sunlight exposure.
Allows wider apertures, effectively decreasing depth of field.
ND2 reduces the intensity by one degree; ND4 reduces two, and ND8 three
ND2: reduces level 1 aperture and 50% light
ND4: reduces aperture by 2 and light by 75%
ND8: reduces level 3 aperture and 87.5% light
Notice
When using the ND filter to the Maximum density,It will appear obvious "X" spot a blur in the picture.
This is a normal optical phenomenon.
Solution:To Gradually lower the density value and reduce the aperture,until the facula disappeared