If you want to experience gloomy, come visit the coast of BC where it rains almost nonstop for 6 months over the winter. :( :( :( We coastal people that were born & raised here are a hardy bunch and not bothered by SAD. :)
To put into context, a 4 foot fluorescent lamp is rated 2850 lumens. I have seen articles in the past talk about using a 4 foot fluor. fixture with 2 or 4 lamps. 50,000 lumens is
much higher than you need, that is *if* it really does produce that. The surface area of the LEDS is MUCH smaller compared to a 4' fluorescent tube so glare is likely to be a big problem. You want the light source to have as large a surface area as possible, which is why indirect light or fixture with opaque diffuser is good. Distance from the lamp(s) and type of light fixture (point source like say a puck light vs linear fixture/lamp) will affect the light level in footcandles reaching the eyes.
Most commercially available SAD light fixtures are rated 10,000 lumens and are placed about 18-24" from the face for about 15-30 mins per day. Mayo Clinic has a good article on SAD and lights
here. Lower output lamps can be used but "therapeutic" sessions may take longer.
Note that "lux" is a metric measure of light level and footcandles is in sq. ft., both in terms of square area. Lux/footcandles on a surface varies as the distance from the light source. "Lumens" is the light output of the particular light source (LED chip/bulb/lamp). The Mayo Clinic article incorrectly refers to a 10,000 lux light fixture as do some other websites I came across.
Or, why not concentrate the light directly where it's needed - on the eyes. Re-timer has these light therapy glasses. Now you can go to the mall, out for dinner or to a movie and improve your well-being without having to sit under a light fixture at home. Think of all the looks and compliments you'd get... :) Also helps for those affected by jet lag, shift work and trouble sleeping.
