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Dr Mike J Smith
Kingston University

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March
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21
 


       

Leaves in Near infra-red

Wed, 21 Mar 2012

During my course on Remote Sensing last year I was trying to drive home to the students that EM radiation is comprised of different wavelengths and that Earth surface features reflect radiation very differently at different wavelengths. Vegetation is a nice example to use because of the dramatic change of reflectance from red to near infra-red (NIR). And you can show this even better by imaging vegetation they are familiar with.

Using my Nikon D70 which is particularly sensitive to NIR I photographed a dead leaf and live leaf in red, green and NIR (below). The postcard (click on it to get a hi-res version) shows each "band" as a greyscale image and you can clearly see the low reflectance in red and green and high reflectance (white) in NIR. The dead leaf still reflects more in NIR, but the difference is far less pronounced; indeed reflectance is nearly equal across all three bands which is why the leaf appears brown in the false-colour composite (bottom right) whilst the live leaf is red.

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