1/100,000,000ths of a second
Discussion
www.rapidnewswire.com/atom.htm
"Due to the extremely high shutter speeds, the image quality and color depth is limited in these photos."
Wonder what Fstop that was...
"Due to the extremely high shutter speeds, the image quality and color depth is limited in these photos."
Wonder what Fstop that was...
robdickinson said:
www.rapidnewswire.com/atom.htm
"Due to the extremely high shutter speeds, the image quality and color depth is limited in these photos."
Wonder what Fstop that was...
Very cool. Seems a little extreme to let off an atom bomb for a photo opportunity though....
All I can find on the interweb is that they were using a things called "rapatronic" cameras, but I can't find any explanation as to what they are. Given they were doing this stuff in the 1940s and they were apparently getting exposures of 1/100 milionth of a second (which is the time it takes light to travel a mere 10 feet) they must have been doing something pretty damn clever.
rich-uk said:It's hard to imagine how they could do it. The bomb is detonated by a mechanical process that creates a critical mass of plutonium. There is no way the timing of that process can be accurate enough to be used to send a signal to the cameras before the bomb detonates to within a few 100 milionths of a second. And you can't wait till the bomb has detonated and then send an electrical signal from the bomb back to the camera, because the light from the bomb would reach the cameras well before the electrical signal would turn up. I can only imagine that the light from the start of the explosion must have been used to trigger the first camera, but it is hard to imagine how you could make a photosensor that could react that quickly. Then again, how the hell did they make an electro-optical shutter that could react on those timescales.
Amazing stuff. I should imagine you have to get the timing quite accurate too, at one frame every 1/100,000,000 second you'd run out of film quickly!
>> Edited by rich-uk on Wednesday 15th February 15:04
I may be wrong, but are we confusing different time factors here?
a. The shutter speed (1/100,000,000 sec)
b. The rate of explosion/rate of expansion of the explosion
c. The rate of "film advance", or frames per second (fps)
I'd suggest that they may have been able to do this by:
Having the camera triggered electrically linked to the trigger mechanism of the bomb. The camera could then have been running a motordrive/auto film advance at (say) 50 fps from fractionally before the bomb went off with a bulk film loader of (say) 500 frames, giving 10 seconds' coverage.
This example would give a time gap between frames of 2/100ths of a second. I don't know the expansion rate of the explosion, but would have thought this may be fast enough to capture the expansion as shown in the photos??
Obviously faster motordrive mechanisms may have been possible (similar to uprated cine film drives). I'd guess the shutter speed may have been achieved by a large fast-spinning disk with a very thin slit in it?
All just a guess of course..
a. The shutter speed (1/100,000,000 sec)
b. The rate of explosion/rate of expansion of the explosion
c. The rate of "film advance", or frames per second (fps)
I'd suggest that they may have been able to do this by:
Having the camera triggered electrically linked to the trigger mechanism of the bomb. The camera could then have been running a motordrive/auto film advance at (say) 50 fps from fractionally before the bomb went off with a bulk film loader of (say) 500 frames, giving 10 seconds' coverage.
This example would give a time gap between frames of 2/100ths of a second. I don't know the expansion rate of the explosion, but would have thought this may be fast enough to capture the expansion as shown in the photos??
Obviously faster motordrive mechanisms may have been possible (similar to uprated cine film drives). I'd guess the shutter speed may have been achieved by a large fast-spinning disk with a very thin slit in it?
All just a guess of course..
simpo two said:
The cameras used a hi-speed rotating mirror drum to aim the light at a strip of equally fast-moving film.
You start it just before they fire the bomb and wait. IIRC the film lasts for about 2 secs.
OK - so that's how they do it - please disregard my previous post then!
simpo two said:Bloody hell. If you made the optical path in the camera something like 10 metres long and needed to deflect adjacent images 2cm apart I reckon your mirror would have to be spinning at something like 100,000 revolutions per second. Even for a small mirror, I'd have thought it would explode ... if the radius of the mirror was 1cm, its surface would be pulling hundreds of thousands of g's. Maybe you can use several rotating mirrors to sweep the image?
The cameras used a hi-speed rotating mirror drum to aim the light at a strip of equally fast-moving film.
You start it just before they fire the bomb and wait. IIRC the film lasts for about 2 secs.
ballsed up the acceleration estimate ... its even worse
>> Edited by ATG on Wednesday 15th February 17:18
and something else here doesn't make sense. If they are getting an exposure every 100 millionth of a second and they can run the camera for 2s ... and lets say each frame occupies 1cm of film, they'd need a roll of film 100,000,000 * .01 * 2 metres long ... which is 2000km of film
>> Edited by ATG on Wednesday 15th February 17:22
ATG said:
I reckon your mirror would have to be spinning at something like 100,000 revolutions per second.
Yes, something like that. It goes bloody fast; I saw a documentary on it years ago.
ATG said:
If they are getting an exposure every 100 millionth of a second and they can run the camera for 2s ... and lets say each frame occupies 1cm of film, they'd need a roll of film 100,000,000 * .01 * 2 metres long ... which is 2000km of film
Not quite, there's a difference between the exposure time and the time between exposures. But they did get through a lot of film awfully quickly!
20,000,000 fps anyone? www.cordin.com/productsfilm.html#RMCombo
>> Edited by simpo two on Wednesday 15th February 17:38
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