Wall color for MoCap system

[Jose Heredia-Jimenez]

Dear members:
What is the best wall color of the lab to use with a MoCap system?
We have always used white walls, without any problems.
I read that blue color is the best option to use with the IR systems/spectrum.
What is your opinion? Any color in particular? (please add pantone-color number)

Thanks

Best,

Jose Heredia-Jimenez
Human Behavior & Motion Analysis Lab. HubemaLab.
University of Granada in Ceuta.

[Joseph McIntyre]

Re: Wall color for MoCap system

Mr. Heredia-Jimenez,

The most important criteria in selecting a color for your walls is what colors/wavelengths your camera's photoreceptors detect. Your camera manufacturer should list the wavelength sensitivity of your camera photoreceptor. As the markers are to be visible against the background of the walls they must be less reflective than the markers in the wavelengths the camera returns high pixel brightness. The cameras can have quite different color sensitivities than our eyes. In my graduate research black cloths used in the lab as covers looked identical but returned three completely different grey scale values. One even appeared brighter to the cameras than a white T-shirt. Those cameras were sensitive to blue. The more blue pigment used the brighter to the cameras it appeared. You will need to view color samples through the cameras to see how bright each color appears. Even colors we perceive as dark may be very camera bright depending on the pigments used.
The second major factor is gloss. Glossy surfaces will reflect light into the cameras. You can get glints and full light source reflections from even true carbon black paint if it is smooth and glossy. Your walls need to have a mat finish. Better yet use a fuzzy surface like felt or carpeting. The object with the lowest grey scale reading I ever recorded was my black Labrador Retriever. Even with his glossy coat he appeared as completely black to the cameras.

Joseph McIntyre
Graduate of the Auburn University Motion Capture Laboratory