Scattering of light

[DM51]

There has been a distracting discussion about the scattering of light in this thread:

Why are warm LEDs preferred by most on this forum?

I posted the following there:

There are numerous reasons for people's preferences for warm vs. cool LEDs (and vice versa); the back-scatter effect of haze/fog being just one of them.

With that in mind, is this thread perhaps getting a little too bogged down here with the discussion of the scattering effect?

Perhaps Rayleigh vs. Tyndall would make a good topic in a separate thread. Just an idea...

... however my post was almost immediately ignored.

I have therefore created a new thread to continue the scattering dscussion, and I'm moving all the scattering posts from there to here.

This is probably a waste of my time, as this thread will not last long if the bickering continues; however it does have the benefit of removing a tiresome squabble from an otherwise useful thread.

 

[Ragiska]

Re: Why are warm LEDs preferred by most on this forum?

They don't. Throw is about surface brightness. Some surface brightness is lost by adding the phosphors thus the same led in cool white will throw better every time.

he was referring to neutral/warm tints cutting through haze, dust, and fog better, which is true

 

[*Dusty*]

Re: Why are warm LEDs preferred by most on this forum?

he was referring to neutral/warm tints cutting through haze, dust, and fog better, which is true

Something to do with the wavelength, thats as far as my knowledge goes I'm afraid.

 

[kito109654]

Re: Why are warm LEDs preferred by most on this forum?

he was referring to neutral/warm tints cutting through haze, dust, and fog better, which is true

He just said "throw better" with no qualifications. If that's what he meant I had no clue. Either way it still doesn't penetrate any farther through those conditions, but it doesn't cause nearly as much glare which makes it easier to see in those circumstances.

 

[Ragiska]

Re: Why are warm LEDs preferred by most on this forum?

He just said "throw better" with no qualifications. If that's what he meant I had no clue. Either way it still doesn't penetrate any farther through those conditions, but it doesn't cause nearly as much glare which makes it easier to see in those circumstances.

which increases the effective distance which YOU can effectively see, which equates to having more apparent throw. so again, he is right.

 

[PayBack]

Re: Why are warm LEDs preferred by most on this forum?

I think the majority is white as possible but the neutral/warm fans are a vocal group. I use both, when it's a nice clear night I use cool but in rain,fog, snow I use warm.

Agree.. the warm fans are more vocal by a long shot, though maybe because they don't have as many options as us white fans.
I prefer white as you often get more light, and when you don't it still looks like you are.

he was referring to neutral/warm tints cutting through haze, dust, and fog better, which is true

Don't agree... they don't "cut through" better as all those particles are too big for the lights wavelength to make a difference.

 

[kito109654]

Re: Why are warm LEDs preferred by most on this forum?

which increases the effective distance which YOU can effectively see, which equates to having more apparent throw. so again, he is right.

Haha, alrighty then.

It's the same thing I've said before several times so we're arguing the same thing. Outside of those conditions, it's not true.

 

[Ragiska]

Re: Why are warm LEDs preferred by most on this forum?

Haha, alrighty then.

It's the same thing I've said before several times so we're arguing the same thing. Outside of those conditions, it's not true.

so as long as you are in a vacuum it's not true. but thankfully we live on a planet with a nice thick soupy atmosphere where it's usually true, especially at night (where you usually need a flashlight) when haze/fog is much more prevalent, especially in wooded/grassy areas, or in caves.

edit:
additionally, the better color and depth perception with a neutral/warm tint also increases the effective range, even in "vacuum" conditions.

 

[PayBack]

Re: Why are warm LEDs preferred by most on this forum?

I think the difference here is he's talking about actual throw, and you're talking about perceived throw.

You're cherry picking a bit by highlight some of what Kito said, but not the important part that support his arguement "he just said "throw better" with no qualifications"

You're now arguing over the qualifications, which didn't exist untill you added them... so cherry picking AND Strawmanning!

 

[Quension]

Re: Why are warm LEDs preferred by most on this forum?

he was referring to neutral/warm tints cutting through haze, dust, and fog better, which is true

Don't agree... they don't "cut through" better as all those particles are too big for the lights wavelength to make a difference.

This discussion has been had before. Regardless of the physics, yellower tints do have a positive effect on typical human vision when it comes to many types of outdoor haze. It's not just light sources; it also applies to filtering under some conditions as well (think sunglasses).

I've yet to see a definitive explanation for it, but the effect exists.

 

[kito109654]

Re: Why are warm LEDs preferred by most on this forum?

so as long as you are in a vacuum it's not true. but thankfully we live on a planet with a nice thick soupy atmosphere where it's usually true, especially at night (where you usually need a flashlight) when haze/fog is much more prevalent, especially in wooded/grassy areas, or in caves.

edit:
additionally, the better color and depth perception with a neutral/warm tint also increases the effective range, even in "vacuum" conditions.

Give it a rest, bro. There is very rarely any fog where I live so I consider it a rare circumstance. It's just another factor that people can take into consideration. You get less glare simply by holding the flashlight away from one's line of sight as well. I prefer the warms anyways; I feel like your at my door trying to convert me or something.

I think the difference here is he's talking about actual throw, and you're talking about perceived throw.

That's a good way to look at it. Our eyes are all different, maybe someone else can more effectively use a cool tint where the glare in fog would bother me and I would be more comfortable with a warm tint.

 

[PayBack]

Re: Why are warm LEDs preferred by most on this forum?

This discussion has been had before. Regardless of the physics, yellower tints do have a positive effect on typical human vision when it comes to many types of outdoor haze. It's not just light sources; it also applies to filtering under some conditions as well (think sunglasses).

I've yet to see a definitive explanation for it, but the effect exists.

I've never disagreed with that.

It might look like it throws better, but that doesn't mean it actually does. A yellow car might look closer than a blue one, but that doesn't mean it is.

This perception bit has just been tacked on the end during the discussion, and wasn't part of the initial premise.

 

[Ragiska]

Re: Why are warm LEDs preferred by most on this forum?

I think the difference here is he's talking about actual throw, and you're talking about perceived throw.

You're cherry picking a bit by highlight some of what Kito said, but not the important part that support his arguement "he just said "throw better" with no qualifications"

You're now arguing over the qualifications, which didn't exist untill you added them... so cherry picking AND Strawmanning!

well, this is a thread about warm/neutral tint led's, so the tinniest bit of logic tells you the "qualifications" will have something to do with tint and color perceptions.

 

[PayBack]

Re: Why are warm LEDs preferred by most on this forum?

well, this is a thread about warm/neutral tint led's, so the tinniest bit of logic tells you the "qualifications" will have something to do with tint and color perceptions.

The point was the original post that started the arguement (not THE OP) was made without qualifications... I don't think it's fair to keep adding them to make Kito wrong, because without them he's right.

 

[bspofford]

Re: Why are warm LEDs preferred by most on this forum?

he was referring to neutral/warm tints cutting through haze, dust, and fog better, which is true

I am a scientist, but haven't got empiric data to prove what I thought about longer light waves penetrating haze, dust, and fog better with control for brightness and focus. It seems that lower frequency light and lower frequency sound penetrate better, and it may be that longer light waves are less likely to hit a particle suspended in the air. Right now we have a lot of pollen in the air after dark in the Colorado mountains, and it has been my subjective observation that warm tint lights throw much better in these conditions. Maybe yellow fog lights are yellow because they throw better in fog, and maybe my ski goggle lenses for snow and fog are pink for a similar reason.

 

[Ragiska]

Re: Why are warm LEDs preferred by most on this forum?

just google "why is the sky blue"

 

[Ragiska]

Re: Why are warm LEDs preferred by most on this forum?

The point was the original post that started the arguement (not THE OP) was made without qualifications... I don't think it's fair to keep adding them to make Kito wrong, because without them he's right.

i thought more about this last night and even with no qualifications kito is wrong. given the same amount of initial light in the same flashlight, the warm tint will indeed put more photons of light on target at any distance due to less scatter in any atmosphere. so given any non-vacuum environment, all things being equal, the warm will always throw further.

 

[gnef]

Re: Why are warm LEDs preferred by most on this forum?

You're still at it?

Your initial assumption is wrong though, given what we know about warm LEDs, they tend to be at least 2-3 efficiency bins away from the cool LEDs, so the cool led is putting out more light total.

It depends on how much is scattered due to the ppm and the tyndall effect, but I would still think that a cool LED will be able to throw at least the same distance, if not further under most circumstances.

 

[red02]

Re: Why are warm LEDs preferred by most on this forum?

You're still at it?

Your initial assumption is wrong though, given what we know about warm LEDs, they tend to be at least 2-3 efficiency bins away from the cool LEDs, so the cool led is putting out more light total.

It depends on how much is scattered due to the ppm and the tyndall effect, but I would still think that a cool LED will be able to throw at least the same distance, if not further under most circumstances.

I'm not completely clear on this, do you mean that no matter what the particles will reflect the light. The cooler LEDs seem to reflect more because there is just more total light?

 

[gnef]

Re: Why are warm LEDs preferred by most on this forum?

There will always be something in the air, either as a colloidal, or as a suspension. If you think of some beamshots, where you can see the beam through the air, what you are seeing is the light scattering from the particles in the air. If there weren't any particles, we wouldn't be able to see the beam, which is why it is easier to see on foggy nights.

If there are particles in the air, it will scatter some light of certain frequencies. Generally speaking, the smaller the particles, the higher the frequency it will scatter, and the larger the particle, the lower the frequency it will scatter. This is why colloids tend to scatter more of the blue, cool side of the color spectrum.

Given enough small particles in solution, it will scatter more of the blue. At that point though, I don't think it really matters much for warm/neutral/cool.

More blue may be scattered, but there is much more light coming out of the cool white emitter. It isn't a simple, this will out throw that, technically, both are true, given different circumstances.

In my opinion (I've done no tests), the cool white will outthrow the warm white in most circumstances, simply due to the higher efficiency of the cool white emitters, even with some scattering of light due to the tyndall effect.