Photo red and beyond leds rarely list lumen output, Cree ones certainly don’t. There are tables somewhere to convert between mW and lumens for different wavelengths, like this one .
Edit:
If such data is accurate (I doubt lux meters/integration spheres are very accurate outside ranges typically measured in lumens ) then we have W = lm / 41.663:
0.5 / 41.663 = 12 mW
9 / 41.663 = 216 mW
36 / 41.663 = 864 mW
That would be valid if the the 660nm was pure like a laser, for a 650nm-670nm distribution I think the 650nm will contribute a bit more to visible output so I expect the lm/W convertion factor to be somewhat higher, but not much higher.
That’s what dedicated threads are for
Mode currents:
(the currents listed in this post are taken from:)
Spectography:
And and with my C01R approximately 150cm away from the wall the hotspot is approximately 65cm wide, at approx 75cm wide it’s approx 33cm, and at approx 37.5cm it’s approx 17cm.
Difficult to measure as there’s a small, smooth transition into spill but the measurements seem fairly linear.
I lightly sanded the front of my optic which worked perfectly for me, now it has a TIR style transition from centre to edges.
(I bought a couple extra C01Rs for gifting, the measurements in the above post were taken with an unmolested one :D)
As for dim, i figured a ceiling bounce with no other lights on would work (especially for the Theodore41!), or just looking at the beam projected onto a white wall.
137 lm/W is nonsense for 660nm, they probably copied the value for 620nm LEDs. The table I linked shows 73.081 lm/W for (monochromatic) 650nm, 41.663 lm/W for 660nm, that’s with 100% electrical to light conversion efficiency. Does the manufacturer datasheet lists the 137 lm/W value?
Edit: You would need to integrate over the 600nm-700nm range to get an accurate conversion factor, but I don’t think you can reach 137lm/W even counting the lower wavelengths. Anyway 620nm and such don’t contribute to the desired effects.
The most accurate way would be measuring it directly, with proper equipment that nobody here owns . Assuming some driver efficiency like 80%, I think estimation from current is more likely to obtain a meaningful value than starting from lumen outputs that normally aren’t used for 660nm.
Medium mode inputs 105mA * 1.33V (NiMH) = 140 mW, assuming 40% total efficiency (60% led * 60% driver+optics) that’s 56 mW output power OTF, 40 mW/cm^2 in 1.4cm^2 area, but that’s a very inaccurate calculation, light distribution is not uniform.
But getting from total output to mW/cm^2 precisly would be too difficult, you need to consider the optics characteristics, that’s why integration spheres are used in the first place. Someone with a lux meter could attempt to calibrate it for 660nm, using a led with similar area and the same optic.
i don’t have my FL yet to see how bright it feels, but here’s my estimate based upon this data.
Using the beam shot diameter over distance we find that the beam has a solid angle of about 24 degrees, so we can use that to find the area needed to match the 40mW/cm^2.
To hit both eyes at the same time with this angle requires the light to be about 24cm or 10” out in front of your face, and this results in an area of illumination of about 78cm^2.
To hit that area with 40mW/cm2 would require 40 x 78 = 3120 mW, yikes that surely seems too high!
The radiant power in the datasheet was about 440mW @ 350mA. Medium mode @ 105mA => 132mW Radiant, and Low mode = 19mW. This is in close agreement with ggf’s calculation of 140mW.
Medium mode at 10” from your face gives 132mW/78cm2 = 1.7mW/cm2.
If the 40mW/cm2 is the power at the face/eyelid/pupil, then for a 5mm pupil this would imply about 8mW into the eye—this seems awfully high to me. A 5mW laser will cause eye damage. This led is not a laser but definitely concentrated over a tight band.
Could the radiant power of the study have been in units of microWatts?
From this it looks like the power was measured right at the 9 x 5mmLed flashlight. Area is 3.8 cm2 for these lights, so the radiant power out the tube was 152mW.
This is another point towards the medium mode of the C01R. Use a diffuser, hold it 10” away and close your eyes.
@Hank, this is from CREE’s site (lamp = LED):
Vision Advisory
WARNING: Do not look at an exposed lamp in operation. Eye injury can result.
Im sitting here waving a 10 lumens red LED at my closed eyes. The light is at arms length (28” away), and it has a double layer of scotch tape for diffusion.
It is WAY brighter than necessary for me to see the light Through my closed Eyelids.
I then turn the light down to 1 lumen, and can still easily see the light through closed lids, still at arms length.
I would not dream of aiming 9 lumens at my open eyeball for 3 minutes… that defies my common sense
Average solar irradiance at Earth surface on direct sun is 1050 W/m^2 = 1,050,000mW/10,000cm^2 = 105 mW/cm^2 according to Wikipedia, so indeed 40mW/cm^2 looks like a large value, of course that doesn’t include the eye focusing effects that make seeing the sun on the sky mostly safe, but looking directly to the sun a terrible idea.
Solar irradiance is 105mW/cm^2 (some it’s IR or UV), so 40mW/cm^2 outdoors probably is not so different when the eye is adapted to bright light. Indoors with the eye adapted to lower light levels it’s a different matter.
Edit: TIL 1 lux = 1 lumen / m^2, so up to 100000 lux from direct sunlight is indeed very bright. I starting to think I need a several thousand lumens flashlight. 1000lm don’t longer cut it.
100000lm from 1m^2 of summer sunlight, that sounds crazy, 7 Emissar D18s on Turbo.
I think lumens are not the best unit of measurement when talking about deep red light for medical purposes.
Lumens measure how much light our eyes can see, not the amount of energy in that light. If you had 1 lumen of pure 650nm light and 1 lumen of pure 680nm light, it would look almost the same, but 680nm would have more than 6x the radiant flux measured in mW.
. Assuming some driver efficiency like 80%, I think estimation from current is more likely to obtain a meaningful value than starting from lumen outputs that normally aren’t used for 660nm.
