When I try upload and calibrate a photo, I get an error message. I am then able to search for my photo which seems to have loaded in spite of the error message, but when I try to calibrate, the calibration won't load and I just perpetually get the spinning wheel of death (the loading symbol). thank you for any advice.
The intensity is not an absolute measure - just a proportion of the dynamic range of the camera sensor. There are a few approaches to correcting for the gain compensation of a webcam, though: #gain-correction -- these should then be able to measure absolute light, though still not measured in lumens, per se -- there are other factors like distance and others that'd have to be considered. This might make a good independent question and I'm sure there are others in the community who'd be better able to answer the question!