> Thermal IR cameras are pretty well established as equipment for e.g. 
> police helicopters to search for or track people (particularly at night).

I'll bet they're damned expensive though. ;-)

> Sound "images" are common for sonar systems. And ultrasound imaging 
> devices, for that matter.

That's not "taking a picture of sound". That's "using sound to take a 
picture". If you want to split hairs, anyway... ;-)

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Invisible <voi### [at] devnull> wrote:
> > Sound "images" are common for sonar systems. And ultrasound imaging
> > devices, for that matter.
>
> That's not "taking a picture of sound". That's "using sound to take a
> picture". If you want to split hairs, anyway... ;-)

Interestingly, you can kind of 'take a picture of sound'. I've seen a couple of
videos on youtube of extremely high-speed film footage (i.e., extreme slo-mo
when played back at 25fps), including one of a car being blown up. As the charge
goes off, you can clearly see the shockwave propagate as a glassy shell.

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>>> Sound "images" are common for sonar systems. And ultrasound imaging
>>> devices, for that matter.
>> That's not "taking a picture of sound". That's "using sound to take a
>> picture". If you want to split hairs, anyway... ;-)
> 
> Interestingly, you can kind of 'take a picture of sound'. I've seen a couple of
> videos on youtube of extremely high-speed film footage (i.e., extreme slo-mo
> when played back at 25fps), including one of a car being blown up. As the charge
> goes off, you can clearly see the shockwave propagate as a glassy shell.

Yeah, Invisible Worlds did this. They detonated a big stack of 
gunpowder, and you actually can see a visible shockwave. It's vaguely 
visible even at normal speed, but in super slo mo it's very clear.

It looks Photoshopped.

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Invisible <voi### [at] devnull> wrote:
> > goes off, you can clearly see the shockwave propagate as a glassy shell.
>
> Yeah, Invisible Worlds did this. They detonated a big stack of
> gunpowder, and you actually can see a visible shockwave. It's vaguely
> visible even at normal speed, but in super slo mo it's very clear.
>
> It looks Photoshopped.

Do you think it only *looks* 'shopped, or do think it actually *is* 'shopped?
I thought it looked as one would expect it to, personally.

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>> Yeah, Invisible Worlds did this. They detonated a big stack of
>> gunpowder, and you actually can see a visible shockwave. It's vaguely
>> visible even at normal speed, but in super slo mo it's very clear.
>>
>> It looks Photoshopped.
> 
> Do you think it only *looks* 'shopped, or do think it actually *is* 'shopped?
> I thought it looked as one would expect it to, personally.

I'm rather surprised that it's a real effect. I thought it only happens 
in Hollywood action films. But, apparently, it's real. Even if it does 
look hard to believe...

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>> Thermal IR cameras are pretty well established as equipment for e.g. 
>> police helicopters to search for or track people (particularly at night).
>
> I'll bet they're damned expensive though. ;-)

Not *that* expensive, we use one in the lab to see the hot-spots on LCDs.  I 
don't think it was more than a few times the cost of a good visible-light 
camera (ie about 3-4K).

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Invisible <voi### [at] devnull> wrote:
> >> Yeah, Invisible Worlds did this. They detonated a big stack of
> >> gunpowder, and you actually can see a visible shockwave. It's vaguely
> >> visible even at normal speed, but in super slo mo it's very clear.
> >>
> >> It looks Photoshopped.
> >
> > Do you think it only *looks* 'shopped, or do think it actually *is* 'shopped?
> > I thought it looked as one would expect it to, personally.
>
> I'm rather surprised that it's a real effect. I thought it only happens
> in Hollywood action films. But, apparently, it's real. Even if it does
> look hard to believe...

Nah, hollywood only tends to do it in 2 dimensions, a ring-shaped wave (which I
believe you can get on water surfaces etc, but that's not what I've seen in
movies!). They also make it too prominent and slow-moving. I'm more inclined to
believe the slo-mo because it is spherical, very fast, and fades very rapidly.
Although of course it might be 'shopped!

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scott wrote:
>>> Thermal IR cameras are pretty well established as equipment for e.g. 
>>> police helicopters to search for or track people (particularly at 
>>> night).
>>
>> I'll bet they're damned expensive though. ;-)
> 
> Not *that* expensive, we use one in the lab to see the hot-spots on 
> LCDs.  I don't think it was more than a few times the cost of a good 
> visible-light camera (ie about 3-4K).

Sure, it's not expensive for suitably large definition of "expensive". ;-)

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>>>> It looks Photoshopped.
>>> Do you think it only *looks* 'shopped, or do think it actually *is* 'shopped?
>>> I thought it looked as one would expect it to, personally.
>> I'm rather surprised that it's a real effect. I thought it only happens
>> in Hollywood action films. But, apparently, it's real. Even if it does
>> look hard to believe...
> 
> Nah, hollywood only tends to do it in 2 dimensions, a ring-shaped wave (which I
> believe you can get on water surfaces etc, but that's not what I've seen in
> movies!). They also make it too prominent and slow-moving. I'm more inclined to
> believe the slo-mo because it is spherical, very fast, and fades very rapidly.
> Although of course it might be 'shopped!

Well, on the example I say, it wasn't spherical at all. The shockwave 
seemed to propogate more quickly along the ground (presumably because 
it's a hard surface?), and was vaguely cylindrical like the tower they 
detonated.

Then there was the smoke cloud reigniting briefly as it escaped the 
shockwave area, "due to the extra oxygen"...

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Invisible <voi### [at] devnull> wrote:
> Well, on the example I say, it wasn't spherical at all. The shockwave
> seemed to propogate more quickly along the ground (presumably because
> it's a hard surface?), and was vaguely cylindrical like the tower they
> detonated.

Ah, I've not seen this one. Sounds about right, tho.

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