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facebookarchive / Surround360

Surround360 is Facebook's open source hardware and software for capturing stereoscopic 3D 360 video for VR. The repo contains hardware designs, as well as software for camera control and rendering.
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how to confirm the color calibration result #227

Closed palfu closed 7 years ago

palfu commented 7 years ago

  1. I‘ve done color calibration of two cameras, with D65 illuminant, while the calibration results of two cameras are a litter different. In the experiment, different cameras may move slightly, this may influence the results? How can I confirm the color calibration results are good?

  2. Both black_level_hole and black_level_y_intercept flags can get black level results, which one is more effective? Looking forward to your reply.

aparrapo commented 7 years ago

Hi @palfu,

  1. This slight shift between cameras is totally fine, it should not cause any issues with calibration. We use a software called Imatest to check the accuracy of the results (it's not free, but they have a trial version). It basically finds the average of each patch and compares it to a ground truth for D65.

  2. You should use black level hole if you have the SpyderCube. This will find the black hole and get the median color. The y-intercept option should be used when there's no physical black hole in the image. This would project the grayscale response of the last row of patches to the y-axis and get the black level from there. Note that this is an approximation and its accuracy depends on how linear the sensor is in the dark areas.

aparrapo commented 7 years ago

Just to summarize my last point, black_level_hole is more effective :)