This test is nowhere near as comprehensive as the big one we did at LEAFFEST a few years ago, but I wanted to know if we could switch Infragram Webcams to red filters as we've begun to do with other Infragram conversions. I set up one of each and ran it through a couple test scenarios, but I'd like to ask folks input on if this seems to be working.
The first is of a bed of weeds in a nearby park. Running with the preset for blue filters, colorized NDVI:
And same but with the red filtered camera, with the red filter preset:
The original image is:
Infragram links:
- Blue: http://infragram.org/i/55661b5ffed547da29000064
- Red: http://infragram.org/i/55661b3cfed547da29000063
I did a second test of a potted houseplant on my back porch:
Blue filter:
Red filter:
Infragram links here:
Blue: http://infragram.org/i/556618eafed547da29000061 Red: http://infragram.org/i/55661939fed547da29000062
One thing I immediately notice is that for areas with low dynamic range data, in dark regions like shadows, the blue filter technique returns lots of artificially inflated values (red artifacts) which likely aren't really high productivity zones, but just noise. The red filter technique does not cause this effect.
It does seem like the red filter version can work with this webcam. But I'd like to hear from others to get consensus.
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I'm confused about which images are photos from the camera and which are NDVI images. It would also help to know what the colors mean in NDVI images.
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These are all NDVI except the third, normal looking one which I labelled "original". Unfortunately a bug in infragram is not allowing display of the unmodified raw images as its supposed to. The scale is the default for Infragram.org.
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