Vernier Software and Technology
Vernier Software & Technology
Tech Info Library

Which digital video camera should I purchase for video analysis?

Consumer-grade electronics such as video cameras change very frequently. As a result we can't recommend a specific make or model, because as soon as we do, that model is replaced by another that may or may not work as well for video analysis. There are two general classes of cameras we recommend for video analysis, and two that we do not generally recommend.

Good:

1) Digital still cameras are probably the best bet, but the video must be manually synchronized with data because they do not stream video.
2) Modern cell phone cameras can often produce good to excellent videos if plenty of light is available to force a high shutter speed. A few Android phones create video files that cannot be read by Quicktime. For iOS, now that we have an app called Video Physics that makes it easy to do basic video analysis:
http://www.vernier.com/products/software/video-physics

Not so good:
3)USB web cameras almost always too slow in both shutter speed and in frame rate. We do not recommend their use at this time.
4)Flip-style cameras are another alternative. A few produce useable videos, but most suffer from a disqualifying flaw: the videos produced use a proprietary codec that QuickTime cannot read.

Finally, if you have older cameras,
5) DV camcorders can yield very good images, and can capture live to Logger Pro synchronized with data collection.

Another consideration is that most new cameras of all types contain CMOS image sensors that suffer from the "rolling shutter" effect. A rolling shutter does not expose the frame all at once, creating a peculiar spatial distortion. It can lead to measurement errors of several percent or even more, depending on the kind of motion and the camera. See an explainer video at https://youtu.be/oETTunUVJio from the Interactive Video Vignettes group. Older cameras that have CCD image sensors do not suffer from this distortion.

More details:

1) Digital Video (DV) Cameras - It is difficult for us to recommend cameras because the manufacturers are continually updating their product lines. For video analysis you need a consumer-grade DV or miniDV camera sold by brand name manufacturers, e.g. Sony, Canon, Panasonic, etc. These cameras typically cost $200 to $300. Get a camera that allows you to manually set the shutter speed to least 1/500 second. Some cameras are too automatic and don't allow you to set the shutter speed. You need to set the shutter speed so that fast moving objects aren't blurred on individual frames. If the camera does not allow you to set the shutter speed, look at a camera that has a "sports" mode. That mode has a fast shutter speed. It is also helpful to have a camera that has manual focus capabilities.

There are two common ways to transfer video to your computer: video stream, and as a file. If you use streaming video, the camera must have a firewire (aka i.Link) port, or a USB 2.0 port that functions as a video stream source. Firewire is more reliable.

If the camera creates files, they must be QuickTime-compatible. Usually a camera that creates "avi" file or a "mov" file can be used, but only a test will determine compatibility.

2) Still Digital Cameras - Most still digital cameras have a movie mode. These cameras can work very well. Look for a camera that lets you specify the shutter speed in addition to frame rate. Sometimes the shutter speed setting is concealed by a "sports" mode setting. In any case, you will need lots of light to force the camera to use a fast shutter. Outdoors is much better than even dual 250 W flood lights. Some cameras offer a 60 or 120 fps mode, which is excellent for many physics applications.

And a final note:
It's very important to test a camera with your computer and Logger Pro to be sure that the file format is compatible with Quicktime, and that you can install the necessary drivers for your camera. (This is generally only a concern with Windows.) We do not recommend buying a camera without first testing it or a very similar model.

Unfortunately the things that make a camera useful as a consumer product are quite different from the very specific needs for video analysis. This means that cameras must be selected carefully, and should be well tested before a large purchase.

See also:
TIL 1925: Logger Pro FAQs for video-related features
Rolling Shutter Effect:
http://livephoto.wikispaces.com/Rolling+Shutter
Desmos demonstration: https://www.desmos.com/calculator/yc9znckbcg

also: https://www.youtube.com/watch?v=dNVtMmLlnoE&feature=youtu.be (this is from Smarter Every Day. Search for rolling shutter)

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