[nudephil (OP)]

Marc has an issue with light for the forum:

Why do I get headaches and eye strain when I referee futsal games with new LED lights? Some say it is brighter than daylight. The light towers are about 16 to 18 meters from my eyes.

Anyone able to help out?

[evan_au]

There is a lot of blue color in the modern "white" LEDs.

This can interfere with sleep/wake cycles, which might give you headaches after a night-time match.
See: https://en.wikipedia.org/wiki/Intrinsically_photosensitive_retinal_ganglion_cells#Violet-to-blue_light

[alancalverd]

The emitting area of a LED is a lot smaller than a filament with the same photon output, so when you look directly at the light you can see an array of very bright spots rather than an evenly illuminated area. This is a known problem with early LED vehicle lights: at a distance, they matched the conspicuity of filament bulbs but up close, the eye responds to the peak brightness and loses night vision.

There's also a possibility of strobing. Filament bulbs have a lot of thermal lag but LEDs may be flickering from full to zero at 50 Hz so your eye is receiving a strobed image of the moving ball and your brain works hard to integrate it to a smooth picture. Movie projectors got round this by adding a shutter, so although the film was moving at 24 frames/second, the shutter chopped the image up to look like 72 fps, faster than the visual response, and the brain more easily interpreted this (plus the fact that each frame was slightly blurred) as continuous motion. 

[RD]

Why do I get headaches and eye strain when I referee futsal games with new LED lights? ...

futsal pitches are shiny, (like a wet road): there's going to be glare when floodlit ....


https://en.wikipedia.org/wiki/Futsal

Polarising sunglasses can reduce glare, but wearing glasses may not be practical/safe when playing football.

[evan_au]

Our street was upgraded to LED lighting a couple of years ago.

One oddity I noted was that each LED in a luminaire (light fitting) casts its own shadow.
So a leaf that used to cast 1 shadow now casts around 6 closely-spaced shadows, giving it a "blurry" look.

Your eyes may be trying to focus on a blurry shadow, which might give you eyestrain?

I suggest you keep your eye on the ball.