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The "Near Infrared Window" of biological tissue demonstrated at a Korean BBQ

Infrared Multispectral
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#1 SteveCampbell

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Posted 10 December 2017 - 22:52


A Korean charcoal BBQ in Visible + Infrared (no UV in the scene).


The coals are throwing off a ton of infrared, which is rendered as magenta in the visible light-calibrated white balance. Due to the "near infrared window" of biological tissue, the infrared light is able to pass right through the steaks, allowing the grill to cast a shadow through the meat.


50mm, f/1.4, 1/800th, ISO6400 (oops)

Full spectrum-converted Canon 5Dmk2 + Canon 50mm f/1.4, no additional filters


I usually wouldn't use a 50/1.4 for IR work due to it's poor performance, but it seems to work fine in visible light-dominated scenes.


Attached Image: IMG_6106.jpg

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#2 Mark

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Posted 11 December 2017 - 10:36

That is interesting. Is flesh really that transparent to NIR, or are the delicious meat strips re-emitting the heat/IR pattern they've absorbed from the grill? Why can't I shine an IR light through my hand? (now THAT would be cool - like a low budget x-ray!) I guess all that water in my body keeps getting in the way, absorbing IR and doing all that other life-sustaining stuff. Maybe if I drink less water... ( ;) ).

#3 enricosavazzi

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Posted 11 December 2017 - 12:00

View PostMark, on 11 December 2017 - 10:36, said:

That is interesting. Is flesh really that transparent to NIR, or are the delicious meat strips re-emitting the heat/IR pattern they've absorbed from the grill? Why can't I shine an IR light through my hand? (now THAT would be cool - like a low budget x-ray!) I guess all that water in my body keeps getting in the way, absorbing IR and doing all that other life-sustaining stuff. Maybe if I drink less water... ( ;) ).
I don't think the meat is emitting NIR radiation on its own, since it would have to be red-hot for this. More likely it is simply transmitting NIR emitted by the coals. I am sure it does emit thermal IR, but the camera used in this case cannot image it.

This meat is typically quite thin (1-2) mm and consists only of muscle and fat. This may help to explain why it behaves differently from a hand.

On the other hand, the appearance of human skin is well known to be difficult to duplicate with artificial materials (or convincingly modeled by simple shading algorithms like those used in computer games to allow real-time animation on ordinary PC hardware) because some of the incident light is diffused through the surface and reflected by underlying layers. This is even more evident in NIR portraits, which usually look "waxen" (wax does behave optically in a similar way).

Edited by enricosavazzi, 11 December 2017 - 12:01.

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#4 Andrea B.

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Posted 11 December 2017 - 16:07

That is such a cool photo !!!!!!!!!
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