3 ms·

It depends on the distance. Even at 1 m an 850 Lumen source with 120 degree radiation angle is painful to look at, and at 1 cm distance the illuminance is 10.00

It depends on the distance. Even at 1 m an 850 Lumen source with 120 degree radiation angle is painful to look at, and at 1 cm distance the illuminance is 10.000 times higher again. The peak illuminance of the sun at the surface of the earth is around 120.000 Lux (Lumen /m2), significantly smaller than such an LED when viewed from a short distance.

Dylan16807 7y ago
I just don't think illuminance is the most important number here. Luminance is more relevant to eye damage in the vast majority of cases, because that measures the spot intensity on your retina. After all, the sun's light would be completely harmless to the eye if spread over a five degree circle, despite having exactly the same illuminance. (Well, you would want a UV filter, but the brightness would be completely neutered.) The sun gets up to 1.6 billion candela per meter squared. 850 lumens in a 120 degree cone, from a 5x5mm surface, is about 11 million candela per square meter if I did the math right. With a retinal danger level around 100 million, you'd need some very strong secondary effects to damage yourself with an 11 million source. Secondary effects like boiling your entire eyeball, or overloading the cornea while the retina is safe. And I don't have the knowledge here to say if that happens, or if your body can easily sink a spread-out watt of light and nothing bad happens.
- ThePhysicist 7y ago
  I don't think that's right. If I hold this LED right in front of my eye the retina will be exposed to the entire 850 Lumen. Sunlight with an illuminance of 120.000 Lux on the other hand yields around 12 Lumen on the retina, assuming a surface of 1 cm². It's the relative distance to the light source that makes this so dangerous.
  - Dylan16807 7y ago
    Even if you only let a pinhole of sunlight in, enough to illuminate a surface to 120 instead of 120k, it will burn your retina. Normal retinal spot burns are not about total light coming into your eye. They're about incoming light per solid angle. A light that is bright enough per area is dangerous at any distance, until it's so so far away it looks like a single point. I'm sure that there's some level at which total light is damaging, even if there are no super bright spots. But that level is going to be significantly higher than 120k. It's maybe a range this LED can reach, maybe not.

Dylan16807 7y ago

I just don't think illuminance is the most important number here. Luminance is more relevant to eye damage in the vast majority of cases, because that measures the spot intensity on your retina. After all, the sun's light would be completely harmless to the eye if spread over a five degree circle, despite having exactly the same illuminance. (Well, you would want a UV filter, but the brightness would be completely neutered.) The sun gets up to 1.6 billion candela per meter squared. 850 lumens in a 120 degree cone, from a 5x5mm surface, is about 11 million candela per square meter if I did the math right. With a retinal danger level around 100 million, you'd need some very strong secondary effects to damage yourself with an 11 million source. Secondary effects like boiling your entire eyeball, or overloading the cornea while the retina is safe. And I don't have the knowledge here to say if that happens, or if your body can easily sink a spread-out watt of light and nothing bad happens.

ThePhysicist 7y ago
I don't think that's right. If I hold this LED right in front of my eye the retina will be exposed to the entire 850 Lumen. Sunlight with an illuminance of 120.000 Lux on the other hand yields around 12 Lumen on the retina, assuming a surface of 1 cm². It's the relative distance to the light source that makes this so dangerous.
- Dylan16807 7y ago
  Even if you only let a pinhole of sunlight in, enough to illuminate a surface to 120 instead of 120k, it will burn your retina. Normal retinal spot burns are not about total light coming into your eye. They're about incoming light per solid angle. A light that is bright enough per area is dangerous at any distance, until it's so so far away it looks like a single point. I'm sure that there's some level at which total light is damaging, even if there are no super bright spots. But that level is going to be significantly higher than 120k. It's maybe a range this LED can reach, maybe not.