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Showing posts from December, 2012

GoPro Hero3 Black Multi-Camera Timing

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In the previous post, I explored the field-of-view of a GoPro Hero3 Black camera.  In this post, I explore the timing of two cameras, both paired with the same remote.  I set the cameras to 848x480 240Hz video, pointed them at a kitchen timer that has an LED blink once per second, and recorded.  Here are four images from each camera, composed together so you can see how the timing varies:



So, accurate to within 2 frames at 240 Hz - only about 8 milliseconds or so of difference.  Should be good enough for my purposes.  The bigger concern is the color shift apparent between them.  Note that the bottom image seems a little more saturated than the top.  Probably correctable, but annoying.

GoPro Hero3 Black Field of View

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I got two GoPro Hero3 Black cameras and am planning a panoramic project with them.  However, to do the project correctly and accurately, I need a good read on their field-of-view.  So, I set up a tripod and a grid and a tape measure, and took a few photos.  Here they are, desaturated and contrast-enhanced, with central red dots and some annotations.  First, measuring the diagonal FOV:


Next, the horizontal FOV:


Finally, the vertical FOV:


The front of the camera lens was almost exactly 17 inches from the grid.  The camera body started about 17.25 inches from the grid.  Assuming the sensor is embedded some distance into the body, I used an estimated field-to-sensor distance of 17.5 inches.  This yields the following field-of-view, in degrees:

Diagonal: 146
Horizontal: 121
Vertical: 93

Doing a little interval math on the field-to-sensor distance shows these angles are accurate to about plus or minus 1.5 degrees.

Interestingly, Photoshop seems unable to correct the barrel distortion of th…