The colour of light reflected by plants

Plants and many animals can perceive “colours” that are invisible to us. For plants, near-infrared radiation just outside the limit of human vision (called by plant biologists “far-red”) plays a very important role. It is possible with modified or special cameras, but also with normal cameras with the help filters to photograph the invisible.

Some years ago, in the summer, I took some photographs in Joensuu with the help of my son Tomás. These photographs illustrate the colour of the light reflected by plants. They were taken with a digital camera (Olympus E-510, 50 mm f 1:2 objective) mounted on a tripod on a day with broken clouds in the sky. The FR photograph was taken with an optical “IR” long pass filter that blocks all visible light and ultraviolet radiation (Wavelengths shorter than 720 nm). The RED, BLUE and GREEN filtered ïmages are just the three channels of the sensor of the camera selected in post processing from an image taken without an optical filter. These four images are displayed in greyscale. The unfiltered colour image is also included for comparison. [Last edited on 2018-01-06]

Full colour

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Summer landscape without filter (RGB colour)

Far-red filter

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Summer landscape with FAR-RED filter

Red filter

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Summer landscape with RED filter

Green filter

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Summer landscape with GREEN filter

Blue filter

"Photo"
Summer landscape with BLUE filter

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