Infrared Vegetation Analysis by Chris Fastie

Canon Powershot A495

Ten snapshots are paired comparisons of the top and bottom panels.
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Adding near infrared (NIR) light to the red, green, and blue channels in a normal photograph allows the spatial patterns of plant productivity to be highlighted. Five photos were taken with a $100 Canon Powershot A495 and the same views were captured with another A495 which records only NIR. (It had the normal infrared block filter replaced with a piece of exposed color negative film that blocks all visible light and passes infrared.) Three combinations of the NIR and one or two visible channels were made in Photoshop and GIMP for each of the five photos, and panoramas were then stitched in Microsoft ICE.
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NDVI (Normalized Difference Vegetation Index) compares the amount of NIR reflected from plants (a measure of how much sunlight is impacting the plants) with the amount of red light reflected (a measure of how much light plants are absorbing to power photosynthesis). The hottest colors (yellow and red) in the lowermost panorama indicate where the most photosynthesis is occurring.
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I was surprised to see that white pines and eastern hemlocks appear to be photosynthesizing as fast as the newly emerging leaves of deciduous trees and grass. I was less surprised to see that rocks and tree trunks are not photosynthesizing much.
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This effort is part of a project of the Public Laboratory for Open Technology and Science (publiclaboratory.org ). There is more information about making this gigapan at fastie.net/?p=1492