Assuming your blue filter is transparent to NIR (near infrared) wavelengths, any red in the image is depicting NIR reflection. The blue filter will transmit visible
wavelengths but only in the blue portion of the spectrum (green and red are absorbed by the filter). So your image should be depicting NIR as recorded by the red pixels
and Blue as recorded by the blue pixels. Green objects (not vegetation) should be quite dark. These are the transmitted/absorbed wavelengths before NDVI modifications are made.
Hope that helps.
Public Lab contributor wangmeising97 just asked a question entitled ' Why we see red image when using blue filter?':
Help them by posting an answer here: https://publiclab.org/questions/wangmeising97/06-05-2020/why-we-see-red-image-when-using-blue-filter
I am using Pi NoIR camera with blue filter for my final year project on NDVI image analysis.
I get the concept of the blue filter will block the red light, while leaving most NIR in RED channel while Visible light will be captured in BLUE channel.
However in this case when the red light is blocked by the blue filter, why the image will reddish in color?
I cant find any explanation, looking for help! Thanks
Below is the image taken by Pi NoIR camera with blue filter.
Here is my NDVI image taken in indoor environment under white led light.
It cant really differentiate the background and the leaf. I have tried using different AWB settings. Any suggestion?
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