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is there a way to distinguish between daylight and artificial light in a room? I'm thinking my options are a light intensity sensor or a color temperature sensor. The sunlight is supposed to be much stronger than artificial light. But I'm wondering if the case will be the same inside a room. Or does the idea seem silly to distinguish between both?

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migrated from stackoverflow.com Jul 28 '18 at 21:23

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    \$\begingroup\$ I'm not a physics expert, but some ideas: 1. The spectrum of sunlight is different from many artificial light sources. Even if the colour temperature looks the same to human eyes, there might be significant differences for many indoor scenarios. 2. Many electric light sources are actually pulsating their intensity at (double) the mains frequency (usually 50 or 60Hz depending on where you live), maybe you could detect that. \$\endgroup\$ – FriendFX Jul 9 '18 at 2:25
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    \$\begingroup\$ Incadescent and fluorescent lights flicker, their frequency is double of AC frequency (100 Hz or 120Hz). Probably, most leds also flicker, check it. If a lamp does not use AC, it does not flicker, of course. \$\endgroup\$ – user31264 Jul 9 '18 at 2:46
  • \$\begingroup\$ This question is too broad. Must the method distinguish all types of artificial light from daylight, or only some? What sensors are available? Filters? \$\endgroup\$ – Beta Jul 12 '18 at 1:23
  • \$\begingroup\$ I think the best thing would be to combine all the suggestions. Look for 100 or 120 Hz mains flicker, check the color temperature (this is conclusive... ) and possibly check the spectrum (seems difficult to me). If I could do only one, I think I would do color temperature. But there are some lights out there with daylight color temperature. \$\endgroup\$ – mkeith Jul 29 '18 at 5:01
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Methods off the top of my head:

  1. Full spectrograph. As others have mentioned the profiles of various indoor lights will all be different than the sun.

enter image description here

  1. Look for UV, the sun has a lot of UV. Indoor lights do not. That's the simplest difference between the sunlight and artificial light.

  2. Monitor the brightness. It's hard to tell because your eyes rapidly adjust, but a sunny day outside is 5-50 times brighter than "bright" indoor lights. The downside to this is that an overcast day, and bright indoor lighting will begin to overlap. https://www.engineeringtoolbox.com/light-level-rooms-d_708.htmlhttps://www.engineeringtoolbox.com/light-level-rooms-d_708.html

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