Blue Smoke near Blair Castle
Smoke usually appears brownish or black, because the carbon particles absorb sunlight. In large amounts, as in forest fires, the air can be strongly reddened. But smoke particles can also be small enough to produce a whitish or blue plume, which is best seen if it is well lit and observed in front of a dark background. This was the case in the image below. Nikon D80, unprocessed, compressed image.
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