# lumens that the human eye can withstand ?



## petrochemicals (Oct 13, 2015)

Hello,

I was wondering if anyone has any information on the ammount of light someone cam look at without it being uncomfortable. On a very bright day you can end up squinting just looking around you, and after doing the dumb dumb of blinding myself a few times temporarily whilst testing the solder on leds I was wondering how much light it takes to be uncomfortable. Im not sure how one would measure this, but from one foot away the 100lumen of the led with a 120 angle was very bright. I can just about look at a cfl bulb but it is not pleasant, where as the old incandesant bulbs would leave me blinded.


----------



## more_vampires (Oct 13, 2015)

Cool question. No simple answer, quite complex.

Shall we start with blue-light hazard? It's applicable to cool white leds.

https://en.wikipedia.org/wiki/High-energy_visible_light#Blue-light_hazard

The type of light is significant. HID, for example, pushes broad band ultraviolet in a similar fashion as arc welding. The infrared component of a light has a different damage mechanism than UV.

http://www.candlepowerforums.com/vb...PF-UV-Hazard-Thread-Protect-your-eyes-and-DNA

The above linked CPF thread and its sublinks contain much information on eye damage, though it primarily focuses on UV. The same general concepts discussed mostly apply to eye damage from light in general.

Diffuse light, such as when you're not staring directly at/into the filament or emitter, is much safer. This is "indirect exposure." You bring up the distance and angle. This too, is quite significant. One thing not yet mentioned is duration of exposure. This is extremely significant.

http://www.ncbi.nlm.nih.gov/pubmed?uid=11692615&cmd=showdetailview&indexed=google
The above is a link to a medical pub concerning eye damage with blue LED at extremely low wattage, but at close range and tight focus. The key to the damage in that publication was the duration of exposure.

So in this sense, "How many lumens can the eye stand?" One partial answer is "almost zero at 90 minutes exposure under the right conditions."

Current pupil dilation is another factor, that is to say if you're eyes are adjusted for the dark it's going to hurt more.


----------



## SemiMan (Oct 13, 2015)

This is a good summary of what is safe:

http://www.cree.com/~/media/Files/C...p/XLamp Application Notes/XLamp_EyeSafety.pdf

What is comfortable is less, and heavily influenced by blue.


----------



## petrochemicals (Oct 18, 2015)

It may have something to do with low frequency light having less energy than hifrequency light.

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

I was working on an xpg warm so not instant but not one for prolonged looking!


----------

