The so called cross-screen filter, or star filter has only limited use but can be worthwhile in particular circumstances. It is generally available in three or four different versions typically know as star-four, star-six and star-eight filters. The star-four filter adds a sometimes dramatic four-flare cross of light to all the highlights or very bright areas in an image. This results in a soft-focus effect with spectacular crosses of light on chandeliers, jewelry etc. The star patterns are generated by a fine diffraction grating or tiny prisms embedded into the filters.A star-four filter is the same thing as a cross screen filter. Each adds four lines of flare, or lines of light radiating from each of the bright spots in an image.
A star-six filter produces six-flare stars of light on highlights, and a star-eight filter produces eight-flare stars. The filters can be rotated to adjust the direction in which the flares form.
Photographers are probably well advised to limit their use of such filters to avoid the effect appearing overdone.