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Old Feb 15, 2016, 7:53 PM   #11
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It's my impression that pure NIR images are colourless, i.e. shades of black and white. Is this also false "colour" i.e. just a colourless manifestation of IR, not any 'purer' than the coloured ones?
Infrared light is outside the visible spectrum. You can't see it. Any representation of infrared light uses a false color, even if that color is white.

Infrared photography detects invisible light and represents it using visible light, like when the invisible man wraps himself in bandages; you don't actually see the invisible man, just the bandages he's wrapped in, whatever color they might be.
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Old Feb 16, 2016, 10:41 AM   #12
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like when the invisible man wraps himself in bandages; you don't actually see the invisible man, just the bandages he's wrapped in, whatever color they might be.
That's a brilliant analogy
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Old Feb 16, 2016, 1:34 PM   #13
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OK, great!
That explains a lot.
So, the term false colour is a misnomer? There's really nothing false about it, it's just one way of representing IR radiation that hits the sensor?
...... john
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Old Feb 16, 2016, 2:47 PM   #14
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'False Color' is the use of visible colors to represent radiation levels which aren't visible to the eye. It's used a lot by meteorologists, who show cloud temperatures in a red to blue scale, when the image comes from an IR satellite camera. Medical profession uses it a lot to represent ultrasound echoes.
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Old Feb 16, 2016, 2:51 PM   #15
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OK great.
Thanks,
..... john
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Old Feb 16, 2016, 3:11 PM   #16
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It's like an X-Ray. You can't see x-rays, but x-ray film reacts to x-rays in a way that is visible.
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Old Feb 16, 2016, 6:24 PM   #17
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... like when the invisible man wraps himself in bandages; you don't actually see the invisible man, just the bandages he's wrapped in, whatever color they might be.
Of course, the Invisible Man I remember is the 1933 film staring Claude Rains. It was B&W, so there's no telling what color the bandages were.
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Old Feb 17, 2016, 10:01 AM   #18
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Hi Tcav,
Yes, of course. They could have been any colour (;-)
Well, the questions I've been asking are centered around the little point and shoot, from which I've removed the IR block filter. But, of course, I still get colour in my images; blue being the most difficult to eradicate. I've been told that developed colour film can be used as a visible colour block, so I've solicited one of the film camera clubs for a piece of same and will see if it works. Some experimenters claim that the film must be 'unexposed' (an odd term - how can one unexpose film) in order to work. I'll let you know how it goes.
... john

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Old Feb 17, 2016, 10:34 AM   #19
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"unexposed" meaning "advancing the film without taking a picture then getting the film developed". In other words, the film is developed before being exposed to light... this piece of developed film would be clear, as opposed to "exposed", where the film is developed after being exposed to light... this piece of developed film would look black.

From everything I've previously read, people use a piece of developed exposed film - the black (visible) colour absorbs all visible light (and reportedly allows IR to pass through).
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Old Feb 17, 2016, 12:21 PM   #20
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I think I would go with an honest-to-goodness IR Passing Filter like the B+W #093 or #092. They're not terribly expensive, and you'll know exactly what you'll get.
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