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This June I am hosting a workshop on data visualization techniques for the physics workshop project. I am presenting video analysis techniques. In our lab we use the excellent unibrain Fire-I camera. This firewire camera produces video at 30 fps and integrates seamlessly with LoggerPro, our preferred data capture and analysis tool. The company has been great about replacing cameras that die prematurely, and produces a superb product. Unfortunately, the MSRP is $119 and the street prices is around $110. We can’t provide one of these cameras to all the participants in the workshop.

I want to give each workshop participant a camera so that they can do video analysis at home. I recently tested 7 different webcameras with mixed results.

Here are the criteria for a good camera for video analysis:

Required:

• Manual Exposure Control
• 30 fps
• Clear image

Preferred:

• PC and MAC compatability
• Higher resolution (640×480 as opposed to 320 x 240)

Camera testing: I asked my daugther to throw a ball straight up in the air. I made a video of the ball and then used the ball to determine the acceleration due to gravity. I was looking for how many frames were dropped, how easy it was to track the object, and how easy the camera software was to setup. Testing was done on a relatively new HP laptop with USB 2.0. Mac testing was done on a new Ibook.

The Cameras:

• Logitech VCam or QuickCam: This camera produced poor images with noticable color problems (Images were yellow) The driver did support manual exposure control, but many frames were dropped and it seemed to produce about 15 fps.
  • Dropped Frames: Poor
  • Tracking Medium (Noticable blur even with exposure control)
  • Device Setup: Medium
  • Mac Support: Yes (macam)
• Flexneck Vcam: Images were medium in quality and color resolution was acceptable. The driver did not support exposure control. Some frames were dropped and it seemed to produce about 23 fps.
  • Dropped Frames: Medium
  • Tracking: Poor (Blur too pronounced to make meaningful measurements)
  • Device Setup: Medium
  • Mac Support: Untested
• 
• Generic Silver Clip-on Camera: Image quality was poor. While there was support for exposure control, it seemed to have little effect on the actual exposure of the image. This camera was only $5.99. Driver installation was somewhat difficult, but probably because it conflicted with the driver from a previous camera. I was able to perform video analysis successfully with this camera, but would not recommend it. About 15 fps.
  • Dropped Frames: Poor
  • Tracking Poor (Poor video)
  • Device Setup: Difficult
  • Mac Support (Macam)
• Xnap webcam: In addition to working as a webcam this camera was designed to interface with a nokia cellphone. It had terrible resolution and image quality and barely managed to capture 15 fps. However, it did work with the cellphone and allow you to take 135×115 grainy images from your phone.
  • Dropped Frames: Poor
  • Tracking: Impossible
  • Device Setup: Medium
  • Mac Support (Untested)
• Kinamax Low Light USB webcam: This camera was a big suprise. The driver did support exposure control and it actually worked well. The camera delivered reasonably crisp images and consistely produced 29 fps! Over several runs there were no dropped frames. It also allows you to turn color off if you are just looking at high contrast images. Definitely the best camera of the bunch.
  • Dropped Frames: Excellent
  • Tracking: Good
  • Device Setup: Medium
  • Mac Support : No Support
• Logitech Quickcam express: This camera produced reasonable image quality and was exceptionally easy to install (A professional installation package!) The drivers were also extremely professional and contained full exposure control that worked well. Unfortunately, it would only produce 15fps and dropped many frames.
  • Dropped Frames: Poor
  • Tracking: Medium
  • Device Setup: Excellent
  • Mac Support: macam
• 
• Generic clipon camera: This camera produced reasonably image quality, but had no exposure control and dropped many frames (15fps). Nothing to recommend it.
  • Dropped Frames: Poor
  • Tracking: Medium
  • Device Setup: Medium
  • Mac Support: Untested

Conclusions:

The Kinamax camera is the best of those tested. It does NOT match the performance of the unibrain, but it is a reasonable tool for doing video analysis of objects moving at relatively slow speed. These sell for a street price of $15, so a lab set will only set you back $120. This is a tremendous bargain to open up a whole new world of experiments. Unfortunately after testing with the latest version of macam, this camera is not Mac compatable. Mac folks might be best off with the Quickcam express or the generic silver clip on camera. (Or just spend the money for the firewire cameras!)