How bright should indoor lighting be to saturate melanopic response?



  • If offices should be brighter, what might be the optimal lux level to saturate a 2h 30m circadian shift? If light boxes are 10,000 lux, is that the ideal level at the ceiling from a chair height measurement?

    Does the ideal lux level drop quite a lot if the light source contains a lot of blue and aqua like Phillips Activiva or similar?

    Should there be a little bit less indoor illumination in the morning vs at noon so the body knows there's q progression of the day?

    I feel like I'm asking questions that not many others have yet asked. I just want the future to be bright whether someone is under a ceiling or outside.


  • f.lux team

    Around 500 lux of daylight (or 1000 lux of office lighting) can saturate the phase-shifting response over 6 hour exposure.

    Here are some possibilities for the 10,000 lux light therapy (5000 lux of daylight) recommendation:

    1. The duration is shorter, so more light is needed
    2. A different brain region is involved, and so more light is needed to entrain mood than "central clock" phase


  • @herf This is quite interesting, only 500 lux is enough for a daylight response. Is the duration to shift the body clocks less when exposed to direct sunlight (80,000+ lux)? How much might the time difference be compared to 500 lux?


  • f.lux team

    @tungsten_smooth Nobody is exposed to 80,000 lux very long because we don't look directly at the sun. 10,000 lux is relative max. It really doesn't go up that much from 1,000 to 10,000.



  • @herf That's quite interesting, I figured it would be more linear. That's really nice to know looking at a 5500 lux sky during the day whether cloudy or blue will be more than enough to shift my schedule.

    One more question, do our eyes need to be open to have a light response (I currently think it doesn't matter)? So if I stare at the sky with my eyes closed, will the schedule shift be the same as with them open?

    I think this is an obvious one as if you could close your eyes to block out bright light responses then that would be more discussed.

    Last question for this topic (so far anyway); What would be the most accessible (easy to purchase either in store or online) most stimulating indoor light that your aware of? Any style, any base etc, as I would like to replace two lights in a ceiling fan if they'll fit (max size is about a 26w cfl, but the socket will handle two 72w halogens).

    I really appreciate all this information as I was thinking I needed over 50,000 lux during noon to really get my schedule in check. It's really nice to know that 1,000 lux early in the morning is plenty. On that note, maybe it's not all about schedule shifting. What about the part where not seeing enough bright light during the day affects how sensitive we will be to light after sundown--is 1-10 thousand lux still enough to mitigate those effects?