prism having a five-sided cross section with two silvered surfaces, giving a constant deviation of all rays of light through 90°, used chiefly in the viewfinders of single-lens reflex cameras, viietahuline prisma kahe hõbedase pinnaga, mis annab kõigi valguskiirte pideva 90° kõrvalekalde, mida kasutatakse peamiselt ühe objektiiviga reflekskaamerate pildiotsijates, prism used to deviate a beam of light by a constant 90°, even if the entry beam is not at 90° to the prism