# Visual Difference Between 2000 and 3500 Lumens



## mikedeason (Nov 8, 2011)

ok I can see a huge difference between my 300 lumen Fenix PD31 and 800 Lumen Fenix TK35.

so I am considering either a 2000 lumen LED or a 3500 lumen HID.

Would the the visual difference between the HID and LED mentioned be similar to the PD31 and TK35?


----------



## Dude Dudeson (Nov 8, 2011)

The basic rule is 4x the lumens to double the brightness, but to actually see it like that you'd need to be comparing identical beam profiles. Once different beam profiles come into the equation it can be different - a throwy 2000 lumen light can have a far brighter hotspot than a more floody 3500 lumen light.


----------



## DM51 (Nov 8, 2011)

Much will depend on the beam profile, as DD has said. With very bright lights such as these, having too much flood can actually be counter-productive and a nuisance. The reason for this is that a floody beam will light up more of the foreground (near you). With a very bright floody light, the foreground could be quite dazzling, and you could find it difficult to see past it and concentrate on objects further away.


----------



## Jash (Nov 8, 2011)

Yes, 3,500 lumens lights up way more than 2,000. As has been said, the beam profile makes a big difference, as does tint and colour temp.

I don't agree with the 4x light needed to appear twice as bright. My TK60 on turbo looks about twice as bright as on high, which it is. There's much debate on that subject and I think it's not an answer set in concrete.


----------



## xul (Nov 8, 2011)

From 
http://www.compuphase.com/electronics/candela_lumen.htm

"The CIE has standardized the relation between luminous intensity and perceived brightness as a cubic root; other sources claim that a square root better approximates this relation."

So it's probably between a (35/20)^(1/2) and a (35/20)^(1/3) ratio.


----------



## Roger999 (Nov 8, 2011)

The 2000lumen LED is most likely going to be pure flood unless it uses an aspheric lens or TIR. Whereas the 3500 lumen HID will most likely be very focused with a smaller hotspot and will look significantly brighter than the 2000lumen LED at a distance.


----------



## Dude Dudeson (Nov 8, 2011)

Jash said:


> Yes, 3,500 lumens lights up way more than 2,000. As has been said, the beam profile makes a big difference, as does tint and colour temp.
> 
> I don't agree with the 4x light needed to appear twice as bright. My TK60 on turbo looks about twice as bright as on high, which it is. There's much debate on that subject and I think it's not an answer set in concrete.



Part of the source of that debate has to do with ranges.

Example: Say you are trying to illuminate something that is simply outside the range of your TK60's high setting. Let's say it's not far outside that range. Now you go to your turbo setting, and now you can see this object. Well obviously here the difference (perceptually speaking) is huge, we're going from "nothing" to "seeing".

On the other extreme, take those same two settings and observe them against a white wall from 3 inches away - well your eye probably isn't going to see much difference in hotspot intensity there. You'd probably see a lot more difference at the edge of the spill than in the hotspot.

It really comes down to how close to the edge of your eye's dynamic range you are - and if you're in the center of that range the 4x rule is pretty accurate. Go toward the edges and that rule starts to bend, get to the edge and that rule starts to break down completely...


----------



## mcmc (Nov 9, 2011)

Also, in addition to the logarithmic brightness response, I've noticed that throwiness seems to actually track in a linear fashion. So while two beams with similar profiles of 1000L and 2000L may not seem like a big brightness jump, in use, I think it tends to come closer to a 2x jump in reach. Anyone else noticed this?


----------



## AnAppleSnail (Nov 9, 2011)

mcmc said:


> Also, in addition to the logarithmic brightness response, I've noticed that throwiness seems to actually track in a linear fashion. So while two beams with similar profiles of 1000L and 2000L may not seem like a big brightness jump, in use, I think it tends to come closer to a 2x jump in reach. Anyone else noticed this?



It depends. If I crank my high-power HID spotlight from low to high, but I'm blasting the foreground with spill, I won't see any better.


----------



## Dude Dudeson (Nov 9, 2011)

mcmc said:


> Also, in addition to the logarithmic brightness response, I've noticed that throwiness seems to actually track in a linear fashion. So while two beams with similar profiles of 1000L and 2000L may not seem like a big brightness jump, in use, I think it tends to come closer to a 2x jump in reach. Anyone else noticed this?



Well, yes and no...

Let's imagine a perfectly collimated laser beam - a beam that never "spreads", even after infinite distance. With such a beam the amount of power makes no difference in the throw distance - the only limiting factor is how much matter the beam passes through. Even at the atomic level there will be both absorption and reflection of pieces of that beam, and eventually that beam degrades to zero.

But if you could have a truly perfect void with no atoms whatsoever then that beam would go forever. Again the amount of power would have nothing to do with it. (But to really get deep there are theories that say various quantum effects over INSANE timescales like that of proton decay {not *photon*} would eventually decay the beam from within.) The inverse square law would not apply for such a beam.

But that's an imaginary beam - we can't produce something like that...

Now let's go to the other extreme, one that DOES exist in reality, a light source that radiates perfectly evenly and spherically (well, perfectly enough for this discussion anyway...).

Now the inverse square law applies "perfectly".

So with our flashlight beams the reality lies in between these two extremes, but it's pretty much going to be a lot closer to the "inverse square law" side of the fence than the "perfect laser beam" side.

Usually the amount of crap in the air is going to be a bigger factor than where on this scale the beam profile lies, but given really clean air I'd say doubling the output with anything besides a well focused aspheric setup isn't going to get you much more than 50% more throw distance at best.

Which rather neatly fits into the "4x the lumens to double the brightness" theory - but again see my above comments about being in the center of your eyeball's dynamic range...

Look straight at the sun, then look straight at another "sun" that's on the other side of our sky and has 4x the output - they're (perceptually speaking) both going to blind you equally because they're both far beyond your eyeball specification. Of course the actual physical damage on your retina will be much more with that brighter "sun"...


----------

