2015-09-06 Links for measuring light PBR CG "Light Measurement Handbook" by Alex Ryer http://irtel.uni-mannheim.de/lehre/seminar-psychophysik/artikel/Alex_Ryer_Light_Measurement_Handbook.pdf "Measuring Luminance with a Digital Camera" Peter D Hisocks 2014 http://www.ee.ryerson.ca/~phiscock/astronomy/light-pollution/luminance-notes-2.pdf "Measuring Light" Peter D Hiscoks 2008 http://www.ee.ryerson.ca/~phiscock/astronomy/light-pollution/photometry.pdf