Green filters, such as the Hoya X1, are used primarily for black-and-white portraiture. They are particularly beneficial when photographing people indoors under tungsten lighting. They give smoother darker skin tones, darker red lips and tend to mask skin blemishes. Skin tones are generally recorded more accurately and vitality is generally enhanced.Reds and blues are rendered darker and greens somewhat lighter. Green filters can therefore be used to lighten green foliage and provide a slight infrared appearance to landscapes.