APPENDICES G: Ring around chart Chart mapping the relationship of filter colour and strength. Strongest filtration is furthest from the centre. Using combinations of filters you can change the colour of light in directions between the main `spokes' ­ for example, choosing yellowish orange (10R + 20Y) or reddish orange (20R + 10Y). Filter values hold good for CC filters used in shooting or printing; also for the relative strengths of filters in a colour head enlarger. To make up red, green and blue use combinations of yellow, magenta and cyan filters. Blue 20B 10C 30B 20B 10M 10B 20B 10B 10B 20C 10B 10C 10B Cyan 10G 30C 20G 20C 10G 20C 10C Green 10C 30G 20G 20G 10G 10G 10C 05C 05G 05B 05Y 10Y 10R 10Y 10Y 10G 10Y 20Y 10R 20Y 20Y Yellow 30Y 05M 05R 10R 10M 10M 20M 10R 20R 20R 10M 30R 20R 10M 20M 10Y 20M 30M 10R Red Magenta 444