I live at 52.5 degrees North. Cosine to the power 4 being what it is, my neighbours and I could be experiencing significantly lower levels of daylight intensity in all seasons than people who live at lower latitudes. In the summer, we will see similar or slightly more daylight integrated over the duration of the day because of the longer days.
The OA does not specify the latitude at which he(? assuming the OA is the site owner's work) is living.
>>keithp+(OP)
Try SAD at 64 North. No picnic. I'd really like to try s light but don't think I'd have the patience to sit in front of one long enough. If it could be made bright enough that you could have it overhead and work at the same time that would be brilliant.
>>keithp+(OP)
Cosine to the fourth power is the wrong formula, it is for camera lenses and takes into account the apparent size of the pupil from both sides, as well as distance attenuation for objects on a fixed plane. Solar illuminance is proportional just to the cosine, no power.
>>alkona+k1
I don't have SAD (well, I don't notice any particular symptoms anyway). One can imagine that luminaires pointing at a light matt surface ceiling would produce an effect like cloudy daylight, but that might just be cosmetic - the science needs to be done I suppose.
>>alkona+k1
I have one of these on my desk, right next to the monitor. Working in front of it for 30-60 minutes a day really helps. Live at 60.5 degrees north. Also take vitamin suppliments and exercise more in winter; it's hard to tell what causes the improvement. With a lamp like this, you don't have to do anything outside of your routine to get more light. You can keep it 20 centimeters (~1 foot) from your eyes, so reduced irradiance due to distance (as this article points out) is not a problem.