What I want to do
I made a simple test two day with my canon two camera setup. Canon 2500 running chdk. Im made two pictures with 720 and 850 nm (easy to find). All the exposure stuff I left two the cameras. Nothing has been changed from default. Cameras are set to produce raw data. Histogram are made with gimp. I was a bit supprised of the 805nm filter. Did not expect that much blue
My attempt and results
Visble 720 nm shot
Visble 850 nm shot
720NM picture
720NM histogram, notice the same red and blue profile!!
850NM histogram, notice the blue and red overlay!!
720NM NDVI
Questions
I expected to see more red with the 850NM. But it seems like the red channel and blue channel are both sensitive to IR. Even with the 720nm you can see that red and blue have the same profile. Only more red. Is my assumption correct. Can anyone explain this??
Based on the result it looks like the 850NM gives better result. Look at the road next to the sign. In 850NM you see more details. Also the whole picture is shifted more to the right on the NDVI scale.
What do you guys, girls think.
13 Comments
Grayson,
The NDVI images look excellent. Just to clarify a few things, I think the following are true:
Some questions for you:
This is a really revealing test. I conclude that:
Chris
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I have pictures of three different kinds: true color, 560nm IR filter, and 720nm IR filter, and I've been having the difficulty of choosing which channel from IR photo to choose. How did you choose? Which channel did you use with the 720nm IR filter? Did you or didn't you modify your IR camera, to take off the IR block filter?
And another question for all you guys, I have to exactly equal cameras, and was considering modifying one. But I am not sure whether to choose the blue filter, or the wratten 25A filter to insert inside the camera once I remove de IR block filter.
Can I close the camera with NO filter, and try them on the outside, like a normal filter?
Thanks Rita
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