why can you not look at a welding flare with your bare eyes but can look at it on tv without eye protection?
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The image on TV is not a welding flare. It’s just a bunch of TV pixels lit by an LED backlight, changing their brightness in coordination to present the *illusion* of a welding flare, based on data recorded by a camera when it looked at a real-life welding flare.
https://en.wikipedia.org/wiki/The_Treachery_of_Images
so it’s a combination of the light intensity and the sparks. in person, sparks entering your eye will damage your eye and cause blindness, burns, etc. same with the light intensity. however on tv, who cares, sparks won’t matter. and the light intensity is limited by what the tv can display, and no tv can be so bright that it can damage your eyes. the light intensity only matters if you’re up close in person (ie the welder) since it encompasses a large part of your field of vision. if you’re further away, then you don’t need eye protection since it’s a smaller field of vision and the light intensity drops off significantly.
Tv panels can output color in the Red/Green/Blue color space, but cannot display infrared or ultraviolet which is beyond human visible spectrum.
When standing (in person) near a welder, the harmful light produced by the welding arc is in a range that is beyond the visible spectrum in the [ultraviolet range](https://sites.google.com/a/coe.edu/principles-of-structural-chemistry/relationship-between-light-and-matter/electromagnetic-spectrum).
We use sunscreen to block harmful UV (ultraviolet) from the sun. Welding can produce UV rays as well that can damage your eyes if protection is not used.
Edit: phrasing and added a fun link!
The really dangerous part of a welding flare is the UV. It will basically give your eyes sunburn (I’ve done it before, it’s very unpleasant).
When your TV is reproducing the picture of the weld it it’s just doing its best to show the visible part of it, it’s not generating the same amount of UV that the actual flame does.
That “doing it’s best” is also important. There is a limit to how bright your TV can make something. The actual welding equipment doesn’t have the same limitation.
A TV doesn’t have enough power built into its display elements to shoot even a moderate fraction of the light from a welding arc. A typical welder has a higher power input than a TV, while the welder pumps that power into a *much* smaller space. Even if you make the (faulty) assumption that both are making all their power into light, the tiny arc from the welder is pumping out much more energy per unit of area than the TV. Lots of light per unit area is one thing that kills your eyes, so there’s your answer.
Welding flare is thermal radiation. The torch gets so hot that it throws off lots of ultraviolet light. UV causes damage to the retina. A TV doesn’t output UV light, so there’s no risk of retina damage.
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