I would like to measure the eye sensitivity to a blue LED when a person is placed in a dark room. I need to convert the luminous flux (lumen) to optical power (W).

Can someone tell me if I should use the photopic or scotopic vision curve?



  • $\begingroup$ You have seen ranges in this wiki article, right? Of course, if you need a more relevant/trustful source, one has to search for it. I tried in this book, but didn't manage to find exact values within 20 minutes of search. $\endgroup$ – Holographist Aug 8 '19 at 12:44
  • $\begingroup$ When slowly increasing the intensity from total darkness, you will initially trigger rods only, not cones. This is scotopic vision. There is just one type of rods, so you will not be able to distinguish between colors. As soon as you start seeing colors, you are leaving the scotopic regime, and soon the cones' response will overwhelm the contribution of the rods: photopic vision. $\endgroup$ – doetoe Aug 9 '19 at 0:29

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