Hoya 58mm C12 BLUE COOLING

Hoya 58mm C12 BLUE COOLING

The Hoya 58mm C12 BLUE COOLING is a colour correction filter designed to adjust the white balance of the image. The Blue Cooling filters correct reddish and orange tints when shooting outdoors or indoors under artificial or fluorescent light. By reducing red and orange tints, blue tones are indirectly enhanced. The Blue Cooling filters are available in the grades C2, C4, C8 and C12, which refer to a mired shift of -20, -40, -80 and -120. The lower the mired value, the less orange and red light enters the lens.

Mired, derived from the term Micro Reciprocal Degree, is a unit of measurement used to express colour temperature. The mired value is calculated using the following formula: Mired = 1,000,000K/T, where K stands for kelvins and T for colour temperature. A worked example: the actual light condition is 4800K; 1,000,000/4800K = 208.3. Your desired colour temperature is 5500K; 1,000,000/5500K = 182. The difference between the mired values is 26, which means you need to reduce the mired value by -26. Using this formula, you can calculate which filter is suitable — in this case, the C2 filter with a mired value of -20 is the best choice.