The B+W 58mm KR-1.5 Skylight Filter is a delicate reddish-yellow conversion filter that absorbs violet and some blue plus a minimal amount of green, but it passes yellow and red undiminished; the colour of the light becomes “warmer” by 15 Mired. That is mostly the optimal amount for correcting the light blue cast in the shadows under a blue sky. It also absorbs UV radiation and hence it provides better sharpness. With colour films and/or developing processes that generally yield results that are too “cool," this filter can be kept on the lens at all times. With this filter, skin tones in particular will be rendered more naturally.