lense color
- Thread starter Axkiker
- Start date
Help Support Candle Power Flashlight Forum
kramer5150
Flashaholic
Pros:
-Quick way to block specific wavelengths.
-Can be reversible and interchangeable.
-No hard wired electrical mods needed to flashlight.
-Many light manufacturers offer filter kits, so no customization is needed.
Cons:
-May add part complexity.
-Reduces lumen output, sometimes significantly.
-Filters ONLY block what wavelengths are there, allowing everything else to pass. They can not boost frequencies in the spectrum.
-Quick way to block specific wavelengths.
-Can be reversible and interchangeable.
-No hard wired electrical mods needed to flashlight.
-Many light manufacturers offer filter kits, so no customization is needed.
Cons:
-May add part complexity.
-Reduces lumen output, sometimes significantly.
-Filters ONLY block what wavelengths are there, allowing everything else to pass. They can not boost frequencies in the spectrum.
Okay so my big question is this.
It seems that anytime you have a colored LED the lumen output is already lower than that of a white LED.
So if you were to use a lens to change the output from say white to blue the output would be less. However would be it any more less than by using a blue LED ?????
Im not sure what you mean abotu boosting frequencies.... Can you explain
thanks
kramer5150
Flashaholic
Filters ONLY "block out", they can not add light. Thats all I meant to say.
So because of this, the lumen output drops. This is how filters work, they block light.
If you have a blue and white LED that measure an equal 100 Lumens, and you place a filter infront of the white LED so that it only passes blue light, its output will be less than 100L. The 100 Lumen blue LED will be brighter than the filtered white LED.
So because of this, the lumen output drops. This is how filters work, they block light.
If you have a blue and white LED that measure an equal 100 Lumens, and you place a filter infront of the white LED so that it only passes blue light, its output will be less than 100L. The 100 Lumen blue LED will be brighter than the filtered white LED.
Okay I think we are getting on 2 different paths....
If we take 2 Led's which are 100w leds one being white and one being blue. The Blue LED will always have a lower lumen output spec than the White. so lets just say the white has 5000lm and the blue is 2500lm
If I take the white led and place a blue filter in front will the new blue output be 2500lm of blue... or are filters not as efficient
May be a dumb question im just trying to figure out if its better to order colored leds or just use colored lenses..
thanks
KeyGrip
Flashlight Enthusiast
That depends on the quality of the filter, and how saturated the color is. There is no standard for how much it reduces light.
What will you be using the light for? There are plenty of good options in each category.
GregWormald
Enlightened
It sounds to me like some research on the physics of filters, and the spectrum output of LED's would be worthwhile.
AFAIK all "white" LED's are already filtered--to make the output look white.
Greg
AFAIK all "white" LED's are already filtered--to make the output look white.
Greg
Nil Einne
Newly Enlightened
I don't have any definite evidence but I think it's rather unlikely the filter would be as 'efficient' presuming you mean if you filter only allowing the same frequencies you'll get the same lumen output. The primary reason why you see lower lumen output from coloured LEDs particularly blue ones is because of the way luminious flux is defined, based on the perception of the human eye.
In fact if you take a look at a datasheet, say the Cree XP-E http://www.cree.com/products/xlamp_xpe.asp , you can see that with Cool White you get 122 lumens at 350mA. With green you get 100 lumens at 350mA. The typical forward voltage is higher, 3.4 vs 3.2 so it's actually 1.19W vs 1.12W but even so if you're getting 122 lumens/1.12W white, do you really think you're going to beat 100 lumens/1.19W green with a filter which only outputs the same select frequencies?
Or take red where you get 56.8 lumens at 350mA. This may seem bad but remember these have a very low Vf, 2.1 typical at 350mA so we're only talking 0.735W. It seems you get about 140% at 500mA for red so you'll expect ~80 lumens. Considering Vf at 700 is 2.3V, 2.2 for 500mA must be roughly right so 80 lumens/1.1W. Again do you really think you'll achieve that with a white LED filtering the same frequencies?
Also if Cree or whoever can product greater efficiency by just using a filter on a white LED, don't you they might just do that? Okay it will increase cost but for those who really want the efficiency.
Note that your filter may allow additional frequencies and in fact this light could in some cases even look the same to the human eye. Or more importantly you may prefer or be happy with the different looking light. This complicates matters somewhat. But if efficiency is the aim, then generally speaking producing frequencies you don't want and filtering them out is unlikely to be efficient.
BTW AFAIK white LEDs aren't filtered much. They use phosphors but that's somewhat of a different concept. My understanding is we were talking about ordinary filters which simply cut off unwanted frequencies. I don't believe most filters are phosphor coated.
P.S. I suspect coloured LEDs are somewhat heldback by the smaller size of market meaning the money just isn't there. Particularly for green, red etc. Blue is perhaps not so bad so I presume some of the white LED research helps this.
In fact if you take a look at a datasheet, say the Cree XP-E http://www.cree.com/products/xlamp_xpe.asp , you can see that with Cool White you get 122 lumens at 350mA. With green you get 100 lumens at 350mA. The typical forward voltage is higher, 3.4 vs 3.2 so it's actually 1.19W vs 1.12W but even so if you're getting 122 lumens/1.12W white, do you really think you're going to beat 100 lumens/1.19W green with a filter which only outputs the same select frequencies?
Or take red where you get 56.8 lumens at 350mA. This may seem bad but remember these have a very low Vf, 2.1 typical at 350mA so we're only talking 0.735W. It seems you get about 140% at 500mA for red so you'll expect ~80 lumens. Considering Vf at 700 is 2.3V, 2.2 for 500mA must be roughly right so 80 lumens/1.1W. Again do you really think you'll achieve that with a white LED filtering the same frequencies?
Also if Cree or whoever can product greater efficiency by just using a filter on a white LED, don't you they might just do that? Okay it will increase cost but for those who really want the efficiency.
Note that your filter may allow additional frequencies and in fact this light could in some cases even look the same to the human eye. Or more importantly you may prefer or be happy with the different looking light. This complicates matters somewhat. But if efficiency is the aim, then generally speaking producing frequencies you don't want and filtering them out is unlikely to be efficient.
BTW AFAIK white LEDs aren't filtered much. They use phosphors but that's somewhat of a different concept. My understanding is we were talking about ordinary filters which simply cut off unwanted frequencies. I don't believe most filters are phosphor coated.
P.S. I suspect coloured LEDs are somewhat heldback by the smaller size of market meaning the money just isn't there. Particularly for green, red etc. Blue is perhaps not so bad so I presume some of the white LED research helps this.
Last edited:
All great info guys !!!!
I agree some research on how filters work and the different types is probably called for on my part.
For this app it probably wont matter much. Yeah efficiency is key however the difference in 5k lumens and 4500 being underwater probably wont matter much to me....
This is however an interesting subject and learning about the process is cool to me...
I agree some research on how filters work and the different types is probably called for on my part.
For this app it probably wont matter much. Yeah efficiency is key however the difference in 5k lumens and 4500 being underwater probably wont matter much to me....
This is however an interesting subject and learning about the process is cool to me...
