Used primarily for black and white photography. XO is highly effective for outdoor portraits because red is rendered dark while green appears lighter.

Great for correcting skin tones, bringing out facial expressions in close-ups and emphasizing the feeling of liveliness. X1 is highly effective for indoor portraits under tungsten lighting.

FOR COLOR FILM:
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.