How bright would a lightsaber be in real life?

The current best “flashlight”-like lightsaber replicas produce about 700 lumens max in the tube, with cutting edge neopixel string LEDs pushing about double that.

Both look fantastic on camera, and look damn near identical to the movies under artificial light and even better in dark conditions. Broad daylight? Not so much. I’m sure that probably has something to do with camera exposure.

However, to the naked eye, they look like solid colored tubes, with no aura. Cool, but pale imitations to the real thing.

One would assume that if Star Wars was real, lightsabers would look like they do in the movies to the naked eye, with its signature very light, almost white core, and colored aura. How bright would it have to be to like that to the naked eye. And would it be so bright that it blinded the user?

And bonus question, is there any current technology that could convincingly replicate that appearance to the naked eye (obviously as a replica). Consider durability not a consideration, just durable enough so that it wouldn’t break while immobile and not striking other object.

I was thinking a neon tube with an extremely high wattage being passed through it, but not sure.

Neon lights are not that impressive in daylight.

Hopefully the day / night settings are better than what I get on my Android tablet.

What you’re looking for is a colored light that’s so bright, that it saturates even the other color receptors, and thereby appears white. Which can work on camera. But I’m pretty sure that anything bright enough to do that to the eye would be so bright in its actual color as to be blinding.

What do you mean?

OK, I’ll bite, what is a lightsaber blade supposed to me made of?

Ugh, Arkcon:, go read Wookiepedia – its a fictitious energized plasma emitted from a handheld energy cell and contained in a magnetic filed.

That’s all fine, but the only plasma I’ve seen a brief sparks, or lightning in the sky far away from me, for an instant. Just how many lightning strikes are in one lightsaber blade? Multiply lightning brightness by that and you have an answer. I mean to say, an answer, however useless, because such a thing is likely so bright no one can possibly duel with it.

You would not want to look at a plasma arc light with the naked eye. There is a reason why welders look through those dark filters.

In general lasers are not very interesting to look at because they don’t scatter light. We used smoke around the setups to photograph laser tables in operation. I guess a saber is so hot it is ionizing the air. So perhaps the lightning comparison is valid.


yeah, I’d think any beam of “light” that is hot enough to cut through the things a lightsaber can would emit so much ionizing radiation it would give the wielder acute radiation poisoning pretty quickly.

And something that hot would likely crisp the wielder within seconds. It’s almost as if there’s no way a lightsaber could exist in real life.

Although, it was a long time ago. Maybe the laws of physics were different.

Why Death by Lightsaber Would Be Much Worse in Real Life! (Because Science w/ Kyle Hill) (Youtube)

Your eyes are logarithmically sensitive to changes in illumination, just like your ears are to changes in audio sound levels. Increasing brightness by 40% is just barely enough to see, yet it requires 40% more actual output, battery drain, etc.

That’s one reason why our eyes can tolerate 110,000 lux on a bright day, yet can still see dimly under starlight at 0.0001 lux. But this also makes it very difficult to artificially create surface brightness under direct sunlight. Your eyes adjust so you don’t perceive the incredible amount of light energy already being reflected off the terrain.

But to compete with that, an artificially-illuminated surface (whether light saber tube or anything else) must be incredibly bright. It wouldn’t blind you in daylight because your eyes are already adjusted. Imagine the sun glinting off shiny chrome on a car – that doesn’t blind you but it looks much brighter than surrounding daylight-illuminated objects.

There are two challenges:

(1) The device must produce tremendous illumination to seem bright under direct sunlight.

(2) The device must constantly sense ambient light and adjust moment by moment, otherwise a cloud passing would blind you. A cloudy day is about 10,000 lux or 1/10th a sunny day. Indoor light suitable for reading is about 100 lux, or 1/1,000th a sunny day outside. This implies the illumination of the hypothetical “real” light saber is just a guide or user aid, not related to its cutting function. It also implies that fantasy device is constantly measuring ambient light and adjusting the blade illumination from moment to moment, without changing the cutting action.

There are 5,000 lumen flashlights and maybe 10,000 lumens is possible. Compared to the 700 lumen device you mentioned that wouldn’t appear 14 times brighter, even given 100% efficient diffusion in a tube.

According to Stevens’ Power Law,’_Power_Law, the visible brightness difference is proportional to the quotient of the cube roots of each lumen output. That assumes a 5 degree-wide beam against a flat target in the dark, but probably is close enough for the light saber approximation.

So comparing 10,000 lumens to 700 lumens:

700^.33 / 10000^.33 = 2.2, or the 10,000 lumen light will visually appear 2.2x brighter than the 700 lumen light.

The forum timed out before I could make a few updates.

Instead of a tube-shaped diffuser over a 10,000 lumen flashlight, maybe a string of high power, outward-facing LEDs mounted on a thermally conductive rod might be possible. A diffuser would still be needed, but the lumen count could be much higher. Unfortunately the power draw and battery required would also be much higher. My gut feel is it might be possible with direct wired power and a sufficiently advanced thermal design (maybe even liquid cooling), but there’s no way any hobbyist could afford it.

The other side of the question is what would a real lightsaber look like on film? Film captures large brightness ranges very differently than our eyes.

Joema gets at the root of the problem.

In the movies, lightsabers always appear as bright as a lightsaber. Turn one on under the bright suns of Tatooine? Looks like a lightsaber. Turn one on in an ice cave on Hoth? Same brightness. In a carbon freezing chamber on Cloud City? Same brightness.

Except that’s not how the human eye works. A lightsaber bright enough to seem like a lightsaber under the suns of Tatooine would be as bright as a floodlight. It would overwhelm the eyes indoors or in a cave.

The reason this works is that in a movie a desert sun is only slightly brighter than a dark cave. It’s just that our eyes don’t notice it. We’re never blinded by the bright sun while sitting in a dark movie theater, because the bright sun isn’t actually very bright. If you suddenly exposed the movie audience to a light as bright as the desert sun, they’d be literally blinded, temporarily anyway.

And so a lightsaber in a movie looks the same brightness no matter what the environment, and that’s physically impossible given how the human eye works. If you adjust your light saber brightness so it looks correct in bright indoor lights it will look blindingly bright in a dark room, and not very light at all under direct sunlight.

Well, I’m not sure what qualifies as “high power” for an LED, but each individual led in a Neopixel strip pulls 60 milliamps, and the high end lightsabers have around 144 leds in it and have shit battery life already (using the best batteries you can fill in a hilt). I do not know how bright the brightest LED is, or how much power it draws, but I can say the one I use as a flashlight on my phone is pretty damn bright.

One of the brightest LEDs is the Cree XHP70, which can produce 4,000 lumens. It is efficient at 150 lumens per watt, but nonetheless pulls 32 watts at full output.

Whether multiple emitters are firing axially down a tubular diffuser or mounted on a liquid-cooled heat sink rod and firing laterally, I think the output is available.

Rapid flux control in response to ambient conditions is also available, Surefire flashlights call this Intellibeam.

That leaves source power, which I don’t think is possible at that level in a sword-shaped handle, even if you used a fuel cell. If you accept wired power and no cost limit to engineer and develop it, it’s probably possible. If you wore a backpack power source like Ghostbusters, it might be possible. I’d personally be afraid to have a kilowatt hr of li-ion batteries on my back while pulling several hundred watts. However that’s within the safe discharge rate.

Hmmm. I don’t think I discounted backpacks in my OP, but I’d sure like to see it! (IRL of course and at a safe distance). BTW, the reputably brightest “flashlight” lightsabers are called “tri-cree” whch I assume means they use 3 of them in the emitter. They can’t do some of the neat effects that some people demand though.

Light sabres are for show. Nonsensical movie-flash. Just like when two guys fence, it is rarely anything like what is portrayed on film. I mean, if you really want to create a effective, powerful plasma claymore, I suspect you would seek the advantage of making the blade as hard as you can for the other guy to see.

sword-fighting as portrayed in film & TV is nothing more than a good way to ruin a sword.