RED:- Gives exaggerated cloud effect, simulates night effect (by slight under exposure). Cuts through ambient UV haze, Gives stark contrast to light coloured buildings against a deep sky. Darkens green lightens reds and yellows.

ORANGE:- Strong cloud effect increases outdoor contrasts. Eliminates UV and cuts through haze. Good for distant landscapes and aerial photography. Enhances the rendering for surface textures on brickwork and stone. Also useful for furniture as it enhances deeper colour woods. Ideal for portraits as it subdues lips and reddish facial blemishes. Lightens red, orange and yellow, darkens blue and green.

YELLOW:- Enhances cloud effect by darkening blue skies. Slightly absorbs UV for haze penetration. Improves contrast for building against a blue sky. Lightens yellow and darkens blue.

GREEN:- Helps contrast for fields, flowers, trees etc, by lightening foliage. Slightly absorbs UV. Helps cloud effect. Darkens suntanned skin, but exaggerates freckles and skin blemishes. Lightens green, darkens orange and red.