I haven't found a good answer to this anywhere --
Coming from the music world, I've known that sound pressure levels from multiple sources do not add up in a linear fashion. That is, if one instrument can put out 100 dB and is joined by another, the result is not 200 dB (thank goodness!).
I understand that lighting measurements are different, and that besides lumens, we've also got candela, foot-candles, lux, etc.
So, do two 600-lumen lights really add up to 1200 lumens? Or do they still add up while measurements of luminance do not add up the same way?
I'm having difficulty finding answers elsewhere because hardly anyone else seems to care about adding multiple light sources -- they usually just describe single sources. There was a similar question posted on a physics forum somewhere from a year ago that hasn't gotten any response, either.