A reflex resp. polarisation filter is used in photography to produce a satisfactory result also in the case of pictures of reflecting non-metal surfaces such as water, glass or smooth plastic surfaces. When photographic such smooth surfaces, unwanted reflections may occur (mirrorings) that cover the main motif. The reflex angle of the filter is set accordingly to deflect the disturbing waves, function of their orientation. The remaining polarised light of the main motif can then reach the film plane unhindered. Even photographing through window panes is possible by means of a reflex filter.
Reflex filters are available as lens accessories. There are linear and circular reflex filters.