What does Star filter do?
Star filters create points of light, like "stars," streaking outward from a central light source. This can
make lighting within the scene take on a more glittering, glamorous appearance. This effect is produced by
a series of thin lines etched into the flat optical surface of a clear filter. These lines act as cylindrical
lenses, diffracting light points into long thin lines of light running perpendicular to the etched lines.
Lines on the filter positioned horizontally produce vertically oriented star lines.