HMC X0 (Yellow/green) 77mm
Used primarily for black and white photography. XO is highly effective for outdoor portraits because red is rendered dark while green appears lighter.

These filters, such as K2 (Yellow), G (Orange), 25A (Red), X0 (Yellow/green) and X1 (Green) are primarilly designed for use with Black & White film. However, they can be used with color film to produce special color effects.