nm...what is it.

I feel a bit silly, but I don’t know what nm means or how to interpret it.
When looking at specs for LEDs, some are listed with lm (lumens, and some are listed as nm.
When shopping for, say, luxeons, some reds are listed with a lm rating, whereas some reds are listed with an nm rating (which is usually higher).
How do I interpret these ratings? I don’t want to be buying infra red, or something, by mistake.


Hmmm. Okay.
Looking at Luxeon rebel, there is a deep red (655nm), 640mW@700mA,
And another red(627nm), 106lm@600mA.
How do I interpret this? Which is brighter?

Not sure, the first is missing the lm count. There is also a decent shift into the near IR band for the first one. I would suspect that depending on the age of the eye and the ambient conditions the first may not be as visible as the second. The second is what I would consider more of a true red.

Brighter is relative to the human eye and what you are trying to see.

For example a 415nm blue light is what will make blood stand out most and make it easiest to see (it shows up as black BTW).

Your vision also plays an important part in what you perceive. Generally human vision is grouped into two categories: color blind, or not color blind but there are a myriad of variations in between.

I know people who are not colorblind but they have a hard time seeing blood from a deer yet it really jumps out for me.

What are you using the lightfor?


nm = never mind :stuck_out_tongue:

nm means nanometer. It is 0.000000001 meters in length. As shown above, it is used to represent the wavelength of light. Meter /1000=mm. mm/1000= um (micrometer)… Micrometer/1000=nanometer. Nanometer/1000=pm (picometer.)

Nm quantifies the color of light whereas lm quantifies brightness. In your examples, 655nm would appear to be a deeper red color than 627nm, but it does not define the brightness, thus you cannot determine the brightness or efficiency of either LED by that number alone.

If you’re more familiar with audio terms, nm can also be thought of as frequency and lm as amplitude/volume. One value cannot be derived from the other. You cannot tell if a 150Hz signal is louder or softer than a 100Hz signal just by the frequency or whether a 90db signal has deeper bass than a 100db signal. Each value defines a different characteristic of the signal.


I’m trying to choose RGBW emitters Here.


It’s not something I know much about so I will be interested in seeing the responses.

Sorry I can’t help.


Mostly, The nm was throwing me off, and I didn’t want to choose infra red by mistake . I’ve just built 12 red LED flashlights, and I’m getting a bit tired of the same old XP-E2.
I might even build a lime green triple for no apparent reason.

Here’s a chart from the LED datasheet comparing their relative output based on current. However, the eye’s sensitivity also varies at different wavelengths, so it’s not easy to say which would appear brighter.


Here’s a chart that appears to identify many of the popular LED wavelengths. Looks like there’s a ways to go before it gets into the infrared region.


Thanks people.
I won’t let nm scare me off anymore.

The terminology of colour leds is a bit different from white leds

The wavelength (in nm=nanometer) of the light wave tells you the colour, a few typical colour leds: 365nm(ultraviolet), 400nm(deep purple), 450nm(blue), 500nm(cyan), 532nm(green), 590nm(amber), 630nm(red), 670nm(deep red), 850nm(infrared).

Then there is optical power: the energy per second that is in the emitted light from the led (in Watt, or milliWatt) the amount of emitted light of many colour leds are given in optical power .

The brightness (in lm=lumen) is something different, it is the optical power of leds corrected for how well we (people) see that particular colour. We can see from 400nm to 800nm, but we see best somewhere in the middle (555nm,=green), and hardly see deep purple and deep red.
100mW of green light (532nm) is 56 lumen, while 100mW of blue light (450nm) is a mere 3.5 lumen.

Because giving the output in lumen becomes less and less useful when the colour of the led is further away from green (in the extreme: the visible brightness of a powerful 365nm UV-led is zero lumen) you see that the output of many colour leds is given in optical power (mW) instead of lumen.

Thank djozz.
I knew you’d show up in this thread. I think it was in your UV threads that I first heard references to this stuff. It was you that put a bee in my bonnet about trying the lime green emitter. What the heck will I do with a lime green flashlight?

I still have my 750 lumen pc-lime C8, and I can confirm that there’s nothing useful about it. :smiley:

Find a margarita. :partying_face:

“nm” = “no more (fear, uncertainty & doubt)”

I can always put the lime in the coconut.