Video photography to study combinations?

Saturated Fats

Saturated Fats

AzB Silver Member
Silver Member
Any 14.1 or 1P players out there that would like to study various combination shots in a rack?

My idea would be to setup a tripod next to the table with a camera arm that would allow the camera to be suspended directly over the rack. You would video the rack as you try various combinations and play back the recordings in slow motion (probably on a computer monitor screen) in order to see what the naked eye is unable to see at normal speed. I don’t imagine it would require really sophisticated equipment like Dr. Dave might use for his high speed videos because I don’t think the playback would need to be as slow for this purpose.

Not being a photography expert, I’ve got a number of questions:
1. What kind of tripod setup might work best? I’m guessing the tripod would have to be able to suspend the camera well over the table and enable it to shoot in a downward direction.
2. How much of camera would it take to capture a video that is sufficient to be played back at a relatively slow speed so that it is easy to see what’s going on with the balls?
3. Anything else needed?
4. How much is this kind of experiment likely to cost?
5. Do you think it would actually work as intended?
 
Saturated Fats said:
Not being a photography expert, I’ve got a number of questions:
1. What kind of tripod setup might work best? I’m guessing the tripod would have to be able to suspend the camera well over the table and enable it to shoot in a downward direction.
2. How much of camera would it take to capture a video that is sufficient to be played back at a relatively slow speed so that it is easy to see what’s going on with the balls?
3. Anything else needed?
4. How much is this kind of experiment likely to cost?
5. Do you think it would actually work as intended?
Click to expand...

1. My guess is what you want is a ball head, mounted to the ceiling. This is the top of the tripod, available at camera stores, and designed for this kind of job. The ceiling is way more stabel than a tripod at those heights.

2. I suspect ANY digital camera recording on digital media (not tapes of various formats). This makes it easier to put the images into the computer. Stick with *mpg, *mpeg, *WMV as capture formats

3. moderm windows media player has slow motion contols built in.

4. Ball head is on the order of $60.

I had given some thought to performing this in moderate light with a small aperture (F/16) and see if a single frame camera with a long shutter speed gives you essentially the same information. That is you open the shutter when the CB is struck, and close the shutter 1/2 second to 4 seconds later. Here, you would se the individual tracks of each ball as it left the rack. You are going to need a focal length of about 15 inches to see the whole table from the typical height of an 8 foot ceiling.
 
My DSLR does 720P @ 60 fps. That's the fastest I know of before you get into specialized equipment.
 
MitchAlsup said:
1. My guess is what you want is a ball head, mounted to the ceiling. This is the top of the tripod, available at camera stores, and designed for this kind of job. The ceiling is way more stable than a tripod at those heights.
Click to expand...

I was thinking that a ceiling mount would have problems with the table lights hanging lower than the camera and would also require a stationary setup rather than a portable one. How about something like a tripod with a camera mounting bar?

tripod with bar.jpg
 
I have fooled around with this a bit and I think a 60 fps camera might not be enough to give you the video quality you want. IMO you need a high speed camera to get a high quality video of what your wanting.

I tried with my 60fps camera and it was too blurry to really show what I wanted in slowmo.
 
Camera

You would definitely need a high speed camera. the mount can be done lots of different ways.

If you get anything setup and recorded share the videos.
 
I'm only aware of one consumer-level camera that might be able to do what you want. The problem you're trying to solve is getting a sufficient frame rate to give you smooth (not blurred) motion while also getting sufficient resolution and picture area to actually see what you want to see.

The Casio Exilim EX-FH100 might be able to do this. It's frame-rate is adjustable up to 1000 frames-per-second. However, increasing the frame rate reduces the picture area considerably; i.e., high speed pictures fill less of the frame than low speed ones. Also, there's an upper limit on fps to get 720p resolution. I don't remember for sure what the limit is, but I think I remember it being 120 fps, which I don't think will give you satisfactory slow motion. My guess is that you'll have to sacrifice resolution to get the frame rate you need to slow things down enough for your purposes. A while back, Amazon had this camera for around $250-$275 including shipping.

Whatever you do, I strongly suggest that before you buy anything, rent whatever you find at an acceptable price and make sure it will do what you want it to do.

(For those familiar with Casio cameras: While this one does have some of the to be expected "oh yeah... it's a Casio" quirks, the image quality is really very good.)
 
Synchronization with a strobe light would permit you to use a relatively "slow" camera operating at 30 frames/second or 60 frames/second.

The key to "freezing" motion is limiting the amount of time a single frame of video is exposed to enough light to produce a high-contrast image. Increasing the frame rate is only going to reduce the blur by a factor of two or (for exotic cameras) a factor of four. That's not enough to capture complex interactions between balls and eliminate blur.

What would really help is a strobe light that will fire synchronously with the camera. (Having heaping piles of cash would probably help, too.) The time during which the strobe fires--the "pulse width"--would be a tiny fraction of a second. Although the camera will still expose each frame for 1/30th of a second or 1/60th of a second, most of the light would be pulsed in something like 1/1000th of a second (one millisecond). This is how we freeze motion to capture images of cars, computer chips, medical products, and other stuff using industrial camera-based robotic systems.

You'll notice that in many high-speed videos the images are noisy and suffer from poor contrast. Even with highly sensitive elements in the camera array, having only 1/10,000th of a second to gather light makes it difficult to light the scene appropriately. The contrast tends to be low.

In hand wavy terms, that 10,000 fps camera needs 300 times as much light as the 30 fps camera. Typically that means you want a really powerful strobe. You definitely don't want to look into that strobe when it fires. (To quote an old lab warning: "Never look into laser with remaining eye.")

Assuming you can find a strobe light of sufficient power, the trick would be synchronizing the strobe with an off-the-shelf video camera. A few high-end cameras allow the triggering of individual frames to ensure the strobe and camera are synched. That is, the strobe light or a controller provides the pulse signal. For a commercial camera, it's a bit more likely you'd have to take a video sync signal from the camera and use that to fire the strobe.

Another option is to control the Exposure Time for each frame. This controls the time during which the image is "exposed" to light. This can solve the problem of blur, but doesn't solve the problem of having sufficient light for the scene. That said, it's the easiest fix, so please check whether your camera has a control for Exposure Time.

If you'd like I can run a few calculations to determine what strobe pulse width you'd need to freeze motion of billiard balls. In short, you need to take the following into consideration:

* the field of view of the scene (that is, the size of the table being imaged)
* the resolution of your camera
* the maximum expected linear speed of the balls (maybe 20 miles/hour)
* the maximum acceptable blur (ideally, about 1 pixel)
 
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