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Sun, even on a cloudy day gives more light measured in lumens than even strongest lamps. Windows filter a lot, so being outside is important. You can use Lux Li
by wafflemaker 4y ago
Sun, even on a cloudy day gives more light measured in lumens than even strongest lamps. Windows filter a lot, so being outside is important. You can use Lux Light Meter app to measure light intensity.
Went outside to compare app results:
Not too bright living room - 10lux
Brightly lit kitchen - 400 lux.
Outside (it's 15:45 in Norway, already getting dark), cloudy late autumn day/early evening - 50lux (which doesn't really prove my point :/)
From memory:
Sunny day, direct sunlight - 40k lux
Cloudy summer day - 10k lux.
A window filters 50-80%
You see that even on a cloudy day you get as much as sitting 20cm from a SAD lamp.
With 10k lux you need approximately 30min exposure before 9 o'clock to keep circadian rhythm from drifting.