NDVI Result
I recently modified an A2300 by taking out the IR filter and finding a gel filter that blocks red light, and lets IR pass. I took two pictures, one with the rosco 2007 gel filter, and one without. NEITHER image has the built-in glass IR filter.
I used this tutorial to do the image manipulation. I hear there are processing tools out there, I'm going to give them a try, and perhaps create a macro for photoshop to make it quicker.
Visible base
NIR base - with gel filter
I then processed the image in Photoshop using two methods. First Normalized Differential Vegetative Index (NDVI) in the image at the top, and then NRG (below) where Near-Infrared, Red, and Green are used to compose a picture instead of the usual Red, Green, and Blue. (Thanks for the great site publiclab! http://publiclab.org/wiki/ndvi)
NRG result
I'm obviously itching to do this with aerial images, but I wanted to throw this out there, and see where I'm falling short. I think the NDVI image begins to show me valuable information (where less IR is reflected) but any tips on improving results is greatly appreciated. Comments on importance of custom white balance are appreciated.
If you have any questions, please don't hesitate to ask! Thanks!
Comments
maxmax states they're using the blue channel instead. Since most plants look green, the amount of photosynthesis on that color is lowest as you can see in their graph. However, at the same time the NDVI is a relative measure?
http://www.maxmax.com/ndv_historyi.htm
Playing around with the levels in Photoshop has the same effect as playing around with sensor resolution and bias. So it's obvious that it follows, if green is absorbed less, you'd get a relatively inaccurate image.
How do u get NDVI without red channel? U will ger NIR\G\B!
But as u know,
NDVI=NIR-R/NIR+R
Take me down to the parallax city
BTW, the slight parallax gives a low budget 3D, just cross your eyes.
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