So the only constraint according to the definition is that luminous efficiency at 555nm (540Thz) is 683lm/W, that looks underspecified.
It’s not being measured at 540THz, it is defined at that frequency. Monochromatic electromagnetic radiation with a frequency of 540THz and a radiant energy of 1 Watt has by definiton a luminous flux of 683 lm.
I got the K1 w/green W1 and I measured it at 730 kcd. It looks bright and looks like 730 kcd to me. I don't see any difference between measurement and seeing it.
A good (consistent and calibrated) “lux meter” should in fact match photopic human eye perception, by definition.
However, if we had an irradiance (W/m²) meter, and measured two light sources that to the eye appeared equally bright, let’s say at 450 and 555nm, the 450nm light would read approximately 20 times higher.
Well luckily “lux” as an SI unit is defined as “one lumen per square meter” so it already incorporates the scaling for human vision that the lumen does… that’s how and why you can convert between the two so easily.
Light that isn’t weighted for human vision is measured in power (Watts) or energy (Joules). These are the units that “radiant flux” (not scaled for human perception unlike “luminous flux”) uses.
yes, very much so, until recently color led output was rated in watts, or parts of it, not lumens, only white was measured in lumens. idk what changed,
however as far as topic is concerned, and what i have actually seen, the same led, xpe2 driven by the same current, in my case 2 amc chips, green does look the brightest. out of all available xpe2 colors i tried, and using same optic will throw farther, why? because it makes more light, due to chemicals used in the green chip itself, it really has nothing to do how we see colors, what rods, or cones are exited, i assume the question originated due to some brands making identical lights in different colors and rate throw differently, so the reason above is why it happens imo. and it is pretty clearly stated in specks, in case of e10, green makes 1000+lm and white 760lm. given that optics and drivers are the same, as well as die size, no reason to think otherwise, lux readings will be higher, and calculated throw will be longer.
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your eyes are most sensitive to green
ie green seems the brightest per watt of light energy power
that is why.
also for a given electrical or light watt, green will again be/seem the brightest
i think the eye is like 10x as sensitive to green, compared to blue or red or purple
yellow is next ‘brightest’
lumens are actually weighted by eye sensitivity
a green watt will be about 794 lumens i think
white watt will be less
red blue or purple as little as 100 lumens per watt of light -energy- power
not exact but the point is, lumens vary with color as well as actual power wle
It is 100% eye sensitivity. Think about it this way. Your eyes are much less sensitive to red than green. Put a red and a green flashlight next to each other with the same “photon” output, same beam profile.
At some distance, an electronic light meter may measure the same # of red photons and the same # of green photons.
You, however, will see much less red light, and will see brighter green, and decide in your mind that the green has greater “throw”.
it is 100% instrument readings from integrated sphere, that is how lumens are measured, as well as lux meter, that is how we get lux readings , the fact that our eyes see colors differently is obviously true, but it does not play any role in ansi distance calculation.
For any decent lux meter the measurement will be weighted somehow, but given how underspecified is the definition, it could use an imprecise curve and still be called a lumen llegaly as long as the measurement at 555nm is correct.
Without knowing the radiant flux of each and if/how the operation of the LEDs for each color is different there is no way that can be said with any certainty at all.
Lux is also weighted for human perception, like I said before that’s the unit inherently uses lumens. Since the FL1 throw weighting is at what range the light still hits .25 lux, it too is weighted for human perception. Now, whether cheap (or any) lux meters accurately measure and calculate the perceived intensity of every part of the visible spectrum is another issue.
lol, but we do know, lumen ratings (measured output) of same led at te same current, but different colors. it is in ace beam specks, it is in led’s datasheets, we know what elements used in leds of each color, and we know, how leds are constructed, and how it differs between colors……. , we have all needed, and relevant info to make that call. it is really simple, green throws further cuz it is brighter. idk what exactly you are arguing about.
Looking at edge examples usually explains this stuff best. Let’s talk about a black-light. It’s very radiant. But not very luminous. It does a poor job lighting a room, so it has a low lumen reading.
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The user manual for my Extech Lux meter has this frequency response spectrum and has a statement about the calibration under a precise Standard tungsten light source of 2856K. i believe this is their weighting toward green to approximate the human eye.
Even though the integrating area of the sensor is only ~14.5 cm^2, the device calculates the lux value for a 1 square meter area. The sensor is an exclusive photo diode & color correction filter, with spectrum designed to meet C. I. E.
Aha, yes of course, that would be the correct explanation thanks. Hmm, does that mean i don’t need to be in a vacuum when using my tape measure?
Yes, that is correct. Unless it is made from kryptonite or poached salmon.
Maybe it has something to do with how efficiently the human eyes process different colors, and also how efficiently the brain processes them
I’m pretty sure the sensitivity difference of the human eye for different colors stems from the fact that there are way more color-receptors (cone-cells) for green than red or blue in the eye. I was told this is an evolutionary thing because there is a lot of green in nature.