HMC coating refers to several thin layers applied to the filter glass. The abbreviation HMC stands for "Hard Multi-Coated". The main task of these layers is to minimize light reflections on the filter surface. This prevents the occurrence of unwanted glares, lens flares, and ghosting in the resulting photograph, which leads to the preservation of high contrast and color fidelity. In addition, the hard outer layer increases the mechanical resistance of the filter against scratches and facilitates its cleaning, as it repels water and grease more effectively.