5

I always have been intrigued by high speed/fps video. And I have looked online how much it would cost to buy one myself. However they are often very expensive, I do not know what the average price range was, but to much for me to buy for "fun".

I recently saw this video which made me realize that instead of reducing the exposure time, you can also influence the lighting within the exposure. However in the video this was used to make high speed photos, which made me think if this could not be used for a video camera. My initial idea was to place multiple cameras around a fast rotating mirror. However this might be dangerous when not correctly balanced.

My other idea was also partially based on an article I saw a few years ago. I want to keep it simple, so instead of using some sort of "filter" to only illuminate certain pixels of the sensor at certain times, I would like to take advantage of the fact that it would be a color camera. This involves a red, green and blue light source, such that each frame would be exposed by each light source for a short moment at different times. After shooting I would need to separate each color layer out of frame and possibly convert it into grey-scale images. This would mean that I would only be able to reach three times as high frame rates, the object, which is being filmed, has roughly the same emission/absorption for all three colors and is not highly fluorescent with "large" stokes shift.

This was a bit of a long introduction, but here are my related questions:

  • Would colored LED's suffice for the different light sources? Such as their spectrum, assuming a Bayer filter sensor is used.
  • Are there any theoretical/technical limitations to this idea? Such as the exposure time, since if this is to small compared to the time between each frame then there would still be a substantial gap between every 3 frames.
Improve this question
4

You could use multiple cheap cameras recording at low fps, but slightly out of phase. Bennett Wilburn talks about this in his 2004 Stanford Doctoral thesis, "High Performance Imaging Using Arrays of Inexpensive Cameras".

Improve this answer
  • 1
    There's video on his website. graphics.stanford.edu/papers/highspeedarray – Jason Conrad Jan 14 '14 at 17:19
  • @AJHenderson Not if two time slices overlap. Say, one camera records from 0ms-1ms, the next from 0.2ms-1.2ms, the next from 0.4-1.4 ms. Then it is - at least in theory - possible to calculate 0ms-0.2ms by filtering. – Anne van Rossum Aug 13 '14 at 19:40
  • @AnnevanRossum - good point, though you'll still be limited a bit by the different perspective since the cameras don't overlap exactly. – AJ Henderson♦ Aug 13 '14 at 20:52
1

This will not work because of the difference in absorption of light. The scene will look completely different lit by different colors of light and thus each of the frames will not fit together in a sequence. There is no shortcut for capturing high speed video, you need a high speed camera. You can get cameras up to about 240fps at consumer price points (look at Lumix (Panasonic) in particular), but much beyond that you need a true high speed camera which is more comparable to the cost of a house than the cost of a consumer camera.

You could use an array of sensors and try to account for the differences in position, but you are still limited to the shutter speed of each of the cameras you use and would require elaborate timing equipment to make sure they all fire in sequence and behave similarly optically.

Improve this answer
  • I stated in my question that this technique would only be appropriate for scenes with: "roughly the same emission/absorption for all three colors and is not highly fluorescent with "large" stokes shift.". If this is the case then it should work right? – fibonatic Jan 16 '14 at 19:13
  • @fibonatic - if everything is precisely neutral grey, then yes, you would be ok. Very, very few things have "roughly the same emission/absorption for all three colors". Even so, you are going to have to manage to coordinate and time the lights and will only triple the frame rate, which for most cameras gets you up to only 180fps on a very limited set of subject matter. One of the 240fps cameras that Lumix makes would probably be a better deal (though I suppose you could try to do it for getting 720fps with the 240fps camera, but your still talking some pretty advanced custom lighting. – AJ Henderson♦ Jan 16 '14 at 19:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.