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UltravioletPhotography

Fading signs in LWIR


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Andy Perrin

As previously alluded to here, signs with different colored text in visible light develop thermal differences that make the text visible during the daytime — but as the sign cools in the evening, it becomes uniform temperature, leading to the vanishing of the text.

 

Shown here is a sign out my window captured in increments of roughly 30 min starting shortly before sunset.

 

post-94-0-66847200-1590993083.jpg

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That's fascinating, Andy.

 

This is outside of my spectral range, so I'm somewhat ignorant. Is LWIR effectively the same as thermal imaging, or is it at shorter wavelengths than thermal imaging?

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Nice Andy!

 

Bernard, that's a complex question.

Short answer: Yes.

Actually any camera, even a UV camera can be used as a thermal camera. Even your eyes. If you look at a red-hot object, you know it's hot. That's how these devices work.

 

To answer you, usuaĺly thermal cameras operate in the LWIR region (~7.5-14 µm), like Andy's one, or in the MWIR region (3-5 µm).

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Andy Perrin
Stefano is correct. In this case it clearly was thermal imaging but “thermal imaging” can happen in visible light also if you take a photo of the red hot burner on an electric stove with a phone cam. However objects near room temperature glow in LWIR wavelengths of 8-14microns, which is what this camera was imaging.
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That was a very interesting demonstration. Thank you, Andy.

 

Last night the SigOth and I were channel flipping and stumbled across a completely goofy series entitled Finding Bigfoot. To keep my comment short about why I actually did watch this for 2.5 hours(!!!), I plead fascination with the Bigfoot search team's use of a FLIR camera to look for Bigfoot "hotspots". The team also traveled to Nepal and searched for the Yeti.

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Finding Bigfoot is hilarious, a perfectly acceptable guilty pleasure to watch. I love how every random rustle in a bush is met with "must be a squatch!" (If Bigfoot existed, these clowns would be the last to find it!)
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I thought Colin already captured a good photo.

Thats his Avatar.

 

Glad you noticed....ha ha

Actually it is a good likeness...

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