We’ve been doing some experimentation with the FRC KOP color sensor and we’re seeing some very strange results. It appears that our green channel is reading far higher than I would expect. The data sheet for the Broadcom sensor seems to indicate that the resolution of each color channel is the same (13 bits read in a 20 bit field) but it does state that it “approximates human eye response with green channel” which makes me wonder if the green is actually higher resolution (given that human eyes are more sensitive to green than red or blue).
Experimenting with various light sources (LED on the sensor, fluorescent overheads in our build space, transmissive via a laptop display), various sensing distances and various angles, we’re seeing pretty consistent results. The green looks almost as if it’s double what we expect but merely halfing the green reading doesn’t always allow us to read all primary and secondary colors accurately. I’m also not keen to hack in a fudge factor without understanding why we need it.
Is anyone else seeing this and can anyone shed any light on what’s up (and point us at whatever math we need to adjust our readings)?
Here are a few examples of raw readings for various color targets generated on a laptop screen:
White: R 302 G 591 B 360 (expect R=G=B approximately)
Red: R 206 G 146 B 33 (expect R=high, G=B=low)
Green: R 72 G 344 B 66 (expect G=high, R=B=low so this is good )
Blue: R 25 G 107 B 273 (expect R=G=low, B=high)
Yellow: R 277 G 482 B 89 (expect R=G=high, B=low)