I thought that a large part of the positive response was due specifically to light in the blue part of the spectrum. Hence blue LED devices, ironically blue lig

I thought that a large part of the positive response was due specifically to light in the blue part of the spectrum. Hence blue LED devices, ironically blue light should help you if you're feeling blue. I used a light meter app on my iPhone to measure the light outside in London on a sunny winter's noon, and that came in at 25 Mlux; suitable for an operating theatre apparently.