The B&W 62 mm Deep Blue KB12 Multi-Coated (MC) Extra Wide Glass filter blocks so much red, orange and yellow that it increases the color temperature of very bright halogen and special photoflood lamps (of around 3400K) to that of daylight. With that kind of illumination, and with daylight color reversal film, the subjects will be reproduced in their original colors.
With weaker halogen bulbs or stronger incandescent bulbs in conjunction with this filter and with daylight reversal film, a residue of "warmth" will be retained for an optimal mood in interior photographs.
B&W Extra-Wide's are special filters for wide-angle lenses. In order to prevent vignetting, the accessory thread on the front is larger
Used to balance daylight film under artificial, tungsten or standard (household) incandescent lighting
80 Series Color Conversion Chart
80A increases color temperature from 3200-5500 degrees Kelvin (commonly used with 3200K lamps)
80B increases color temperature from 3400-5500 degrees Kelvin (commonly used with photoflood lamps)
80C increases color temperature from 3800-5500 degrees Kelvin (commonly used with flashbulbs)
80D increases color temperature from 4100-5500 degrees Kelvin (commonly used to remove extreme orange or red)