The cokin warm 81a colour filter is for use with a film camera using daylight colour film or a digital camera in automatic mode colour correction filter which decreases the colour temperature from 3400k to 3200k makes it more red to reduce the blue cast and warm up the tones the warm 81a colour filter is great for landscapes or portraits to warm up the skin the 3 filters 81a 81b 81c can be combined with each other for maximum effect