RPM based on light or color?

[Jens Noriʇzsɔɥ]

Have you tried “Camera Spectrum: Brightness”? RPM is shown at the top. It works surprisingly well even with rather low contrast. The frequency resolution of the FFT is (acquisition rate)/(number of samples) or 1/(time span used for the FFT) – if that‘s ok…

“Camera Spectrum: Color” could also be implemented that way, however, the title could be really easily misunderstood…