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Digital Video Capture and High Frame Rates?
Jeff asks: "So the folks at a place called Conniption Films (great name) developed a camera called the Millisecond Camera which can shoot 12,000 frames of film a second. I read the article and thought 'Hmm that's neat' but then realized they were still using an analog process for shooting this highspeed film. Being a geek, not necessarily into the film side of things but curious nonetheless, I wonder, shouldn't a computer be able to do a better job of such a thing? They say the film runs around a spindle going 500 mph (!). Wouldn't that be prone to failure and use alot of energy? Wouldn't it be more appropriate, easier, and overall cheaper to just hook up a high res CCD to a beowulf </duck> cluster of 2 ghz+ machines and capture high speed images that way? Why hasn't it been done yet? Or has it and I haven't seen it yet?" I did a double-take, when I first read this question, and then got curious and did a little digging. Turns out, high frame rates are not exclusive to the analog photography world, and to illustrate my point, I provide this link. It's woefully short on details, and the explanations as to why a camera that can record 1M frames per second is limited to a playback of only 103 frames, but the technology is out there. Has anyone seen any other digital cameras out there with high frame-rates? What visual mischief could you aspiring photographers get into with such a camera?
A quick calculation on the bandwidth of capturing 12000 SVGA-resolution full color frames per second:
1024 (width) * 768 (height) * 4 (32-bit color) * 12000 (fps) = 377,487,360,00 bytes/second (35 Gbytes/s)
So no wonder they use film...
also consider that most of the time, people that are interested in such frame rates, are also *very* interested in having detailed high-resolution frames of the event at 'interesting' times.
This probably means having to shoot images of around 4-6 megapixels, and I really don't see any way of doing that at the speed needed for this kind of application.
The only way might be exactly what the poster of the topic didn't grasp: have a camera that can take 100-1000 pictures at a 1Mpics/sec frame rate and store them in ultra-fast local memory, and transfer them out at leisure, with a good triggering setup, 100-1000 microseconds worth of data might just be enough for certain applications.
-- the cake is a lie
At 640x240x24, you're talking 7372800 bits per frame. At 1000 frames/second, we'd need to be transferring 7Gbps. That would be a bit hard to handle. You could cut the rate by dropping colors. At B/W, it'd be pretty manageable, but that's probably not what you want. You probably also want higher resolution. No matter what, you wouldn't be able to swallow the stream for long.
Oh, and by the way. The confusion about a million frames/second versus 103 was just poor word choice in the article. What they mean is a 1 microsecond shutter speed - 1 microsecond frames with 9707 microsecond gaps. Great stop-action to cut blurring, but manageable transfer rates.
You can get around any bandwidth issues with a sufficiently large amount of cabling. The whole idea of doing this in parellel implies that. Anyway, compare the bandwidth of digital photography with the physical bandwidth of looping film through an eyepiece at 12,000 frames per second and you come up with a very different problem -- you've got to use TINY film, with an effective resolution much lower than what some of you linux numbercrunchers are assuming. "SVGA resolutions?" Think more like 320x240 -- and don't expect more than a few seconds per cannister, high costs, etc.
.000083 s. With low light, you need extremely sensitive equipment to even detect it and even more sensitive equipment to detect the subtle variations in wavelength that make up colors. Today's CCD cameras are very slow to register intensity light -- much slower than film. The chemical reaction in film triggered by exposure can be controlled much better, simply by changing the tolerance of the film -- which is why your high end, high speed shutter digital cameras are so godawful expensive. The $2500 Canon I've been looking at has roughly the same shutter speed as an equivalent $300 film camera. The extra price is NOT a "coolness" tax...it's for the set of three extremely high res CCD sensors and the chips capable of processing their information at that speed. My film prof used to say "digital ain't digital"...there's a quality factor of all digital electronics that can be poiled down to the quality of interpolation, quality of the ADC and of transistors leading up to it.
No, the problem is light itself. You don't get much of it captured with a shutter speed of
CCD kind of sucks, man. For all its glorious promise, the best CCD chipsets aren't all that much better than the wonderful X-10 spycam.
Hey freaks: now you're ju
Look at it this way, 12000 / 30 / 60 = 6 2/3, so it would take over 6 1/2 minutes to watch 1 second of video at regular framerate. The events of interest here are likely to be much less than one second. You could fit 0.1 seconds of video into a 32-bit address space. 0.1 seconds doesn't sound like alot, but it's way more than enough time to watch a bullet pierce a playing card.
Mechanically inclined.
When was the last time you even heard that phrase? We live in a physical world. A mechanical device is a perfectly acceptable solution to a problem. Not everything needs to be done with software. Just look at the guy's level of disappointment. "But there has to be a way to do this with electronics! Electronics are always better than mechanics, aren't they? It's impossible for mechanics to do something electronics cannot, ins't it? Hello?"
And Cliff's additional writeup is no help either. The reason the video in the example he found can only played back at 103fps is fully explained in the link he provides (and apparently didn't bother to read). Also, the 12,000fps film camera that got everyone talking in the first place not the first of its kind. High-speed film cameras have been around for decades. The real kicker is Cliff's silly statement at the end, which makes it sound as though an electronic high-speed camera would be the first high-speed camera ever. He says, "What visual mischief could you aspiring photographers get into with such a camera?" Gee, I dunno Cliff, how about the exact same things people have been doing with high speed film cameras for the past 50 years, eh?
Sheesh. The world goes beyond the bits in a CPU. Turn off the computer and take a look around at the tangible, physical world.
Free Hans!