With double the strength of the KR3 (81A), the Bay 50 KR6 (81EF) Color Conversion Filter from Heliopan leads to neutral color rendition in strong haze or in the mountains above 2500m (8200'). Even though the human eye automatically adjusts to various lighting conditions, film does not. Irrespective of the light source, a white sheet of paper will always "appear" white to the human eye. However, when photographed under various lighting sources, the paper will reproduce a representation of the light it was shot under. A KR6 filter will allow you to correct for this white balancing problem when you wish to reduce the color temperature of the shot and bring your tones back to a more acceptable level. In addition, this filter is particularly effective when you wish to go in the other direction and make a warm image even warmer - such as a photograph on a beach where you wish to bring out the feeling of heat even more.