The Heliopan 60mm Yellow Green Filter is a basic contrast filter, primarily for use with black and white film, that moderately darkens blue and red tones, lightens green tones, and helps to subtly increase overall contrast. It also helps to better simulate a natural tonal response when working with panchromatic film under artificial lighting conditions. There is an approximate 2x filter factor with this filter, requiring an increase of 1 stop for normal exposure.