HOYA 0991 - Camera filter

Each Hoya filter is the result of research, know-how and complete precision facilities backed by full quality control.\n\nBefore production starts, controls are first programmed into a computer. Then the finest materials are carefully mixed by an automatic V-blender for absolute uniformity. After being melted with highly sophisticated equipment, this material is then precision molded with automatic direct pressing equipment. The pressed blanks are next slowly and continuously cooled to remove strain, and are then polished by high-speed, double-surface polishing machines that assure precise surface quality and perfect flatness.\n\nNext is the coating process which improves the filter light transmission ability. And the transmission characteristics are checked by Spectro-Photometer, after which an ultrasonic cleaner removes all foreign matter from the surfaces. Only after passing all of Hoya's quality tests are the filters assembled, finished and made ready for shipment to customers throughout the world.