These are light balancing filters used to decrease the color temperature slightly for a warmer (redder) tone.
Corrects the tendency toward bluish tones. For example, the 81A should be selected when using tungsten Type B color film (3200°K) with photoflood lamps (3400°K) These filters can be used together.
HMC ( Hoya MultiCoated)
These popular filters are renowned for their ability to minimise reflection at the filter surfaces which reduces flare and ghosting. The result is an average light transmission of over 97%, giving sharp contrast and well balanced color. HOYA HMC filters are recommended for enhancing the performance of today's multicoated lenses.