Blue Light at www.japanese-home-gardens.com

Because Clerk Maxwell added red, green, and blue light together, this technique is called additive. An equal addition of the three colors forms white; red and green add to form yellow; red and blue, magenta; green and blue, the blue-green known by photographers as cyan. It is important to bear in mind that this theory holds true only for colored light; the mixture of pigments is another matter.

To get back to equipment needs for exteriors—you should have several filters. The Wratten K2 (medium yellow) is standard, of course, for correct monochromatic rendering of colors on the panchromatic film which you will use exclusively. The Wratten G (yellow-orange) darkens a blue sky more dramatically and will be highly useful. The X-l (light green) darkens a blue sky and also lightens and brings out texture in foliage. On rare occasions, too, you might use a Wratten A (light red) for extreme over-correction, or rather distortion, as to show a blue sky as almost black.

The properties of light passing through seawater determine the colour of the oceans. Radiation at the red or longwave end of the visible spectrum is absorbed near the surface of the water [9] while the shorter wavelengths (blue) are scattered, giving the sea its blue colour. The depth to which light can penetrate is important to marine life. In clear water light may penetrate to 110m (360ft) whereas in muddy coastal waters it may penetrate to only 15ni (50ft).