• Ultraviolet Photography

SWIR-NIR tri-color snow

Infrared SWIR Multispectral TriColour
5 replies to this topic

#1 Andy Perrin


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Posted 18 December 2020 - 20:36

Here's a tricolor of snow on a window.

The filters are:
780BP30 - red channel
1064BP25 - green channel
1500 long pass (but probably 1500-1550 effectively because of the camera gain fall off) - blue channel

The color channels are BGR essentially because it made the snow stand out better. Alternative is to have magenta cyan snow in RGB.

Attached Image: window 1500-1064-780 RGB_res.jpg

Attached Image: window vis.jpg

Individual frames:

780nm ("red")
Attached Image: window 1500-1064-780 R.jpg

1064nm ("green")
Attached Image: window 1500-1064-780 G.jpg

1500nm ("blue")
Attached Image: window 1500-1064-780 B.jpg

Edited by Andy Perrin, 08 April 2021 - 18:06.

#2 Bernard Foot

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Posted 18 December 2020 - 21:48

Just had a play with your colour separation images!

Actually, if by RGB you mean 1500=Red, 1064=Green, and 780=Blue, you get cyan snow and a magenta wall.

You get magenta snow with 1064=Blue, 1500=Green, 780=Red (GRB ?), which gives a yellowish wall, and 780=Blue, 1500=Green, 1064=Red (RBG?), which gives a cyanish wall.

A magenta-ish wall would probably be my choice because it's nearest to the natural red brick, which would give a choice of yellow snow (as in your image) or cyan snow (which you might see as representing coldness).

Looks like your neighbour (or is it you?) is using plastic film as double glazing - is that effective at the low temperatures you're obviously experiencing?
Bernard Foot

#3 Andy Perrin


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Posted 18 December 2020 - 22:08

Re the plastic film - Probably not, Bernard!

#4 dabateman

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Posted 18 December 2020 - 22:25

Plastic is placed on windows mainly to cur down the breeze as most seem to leak like crazy. I used to put up plastic, it helped a lot. Now not allowed.

Great series Andy.

#5 Stefano


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Posted 19 December 2020 - 00:55

Andy, very interesting. That 1500 nm image has beautiful black snow. I personally like to represent things in RGB when doing tri-color images like this one to keep the analogy with the visible spectrum, but then anyone can mess with the colors as he/she likes.

Very nice that you are using your TriWave again. You took a SWIR selfie, you imaged snow, you imaged flowers and now there is only one big thing remaining for me: a nice glass of black water.

#6 Andy Perrin


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Posted 19 December 2020 - 01:42

Stefano, I tried it the RGB way first, but decided I didn't like the effect. Yellow is visually much brighter than cyan (or magenta for that matter) and it looked very dim to me. The yellow stands out well.