Among variety of filters cross screen effect filters or star filters are often staying behind the screen. But in fact these kind of filters are very unique and have power to completelychange your image. So, what are these cross screen filters for? Looking through photos you might notice lights that are creating a cross of 4 or 6 rays around some points of light sources. The image is very romantic and impressive. As a rule, this effect is achieved by making aperture size as small as possible. This creates crossing lights coming through diaphragm blades. Sometimes this effect looks cool.
But due to some inconvenient conditions like dark places closed diaphragm cannot be implemented effectively. Moreover, cross lights may not appear as you desire.
For this purpose cross screen filters are the most effective way to express your intentions. The secret is in many scratches on the surface of the filter glass. The scratches change refractions of the light as you want. Cross screen filter has a rotation ring. It means that filter can be rotated so the direct on of the light can be changed.
Cross screen filters may be 2, 4, 6, 8 and more. Number means how many rays filter can reproduce. The most optimum number of rays is 4. Cross screen filters are mostly demanded during festivals or winter holidays when the streets are full of illumination.
For sure cross screen filters are important along with C-PL and ND filters.