E21A Color Test with surprising result

My sm653 Wizard has a much higher CCT with the bare LEDs measured head on than it does with an optic.

Turbo 2
CCT = 8792K (Duv –0.0082)
Color Rendering Index (Ra) = 93.4 [ R9 = 78.4 ]

Main 3
CCT = 7950K (Duv –0.0031)
Color Rendering Index (Ra) = 95.8 [ R9 = 87.2 ]

With the optic, the hotspot is 7301K and 6819K on the same levels, respectively. Sounds like your LEDs are behaving normally.

Forgot Joshk tested the LED at max 2A. That’s beyond the 1400mA limit for E21A. So, that’s normal. Maukka tested the LED according to Nichia’s binning current at 700mA.

[Clemence]

I got the Fluke out and perfected the Amps at 700 and ran the test again. Then graphed it all together.
—0 Degree 700ma—
CCT: 5949
Duv: –0.0058

—45 Degree 700ma—
CCT: 5390
Duv: –0.0017

When you put that in an optic or reflector or integrate the measurement it will probably end up being about 5000K.

I sure hope so. I’m learning as I go. Thanks to everyone for the help.
To be continued…

Would like to see the 90 degree measurement. In order to average to 5000k somewhere else in the beam would have to be less than 5000k.

The CCT measurement near 90 deg is 4700K, but it’s not all that bright out there.

Does this mean Fet drivers are a bad choice or is 1400ma average current OK?

Depends, what cell are you using? Quad E21A behind a 10440 would be fine. Behind a high drain 18650 with springs and all bypassed might not.

Haven’t built the light yet. Thinking about converting an old srk style light into a mule using the existing led board.

With and without optic or reflector makes a very big difference in both CCT and tint. Here are two examples with the SST-20 4000K. Bare emitter is always much cooler.

There are just so many variables.

Like the current, and the angle at which you measure the bare led. A diffuser like dcfix will average it somewhat but will still only catch and diffuse less than half of the light. Moreover, a any diffusor causes loss of blue light and warms the tint because of blue scattering more than the other wavelengths. Using optics selects other parts of the light again.

The only way to measure average tint is with an integrating sphere coupled to a spectrometer. It integrates the full 180 degrees of output and the sphere can be characterised by measuring the colour-specific light loss over the spectrum and correct for that. Maukka is the only amateur I know of to have that setup and post results with it.

Update, I got a reflector in the mail yesterday for another project that happens to fit the E21 perfect. The results are much improved.

CIE

Did this particular TIR lens, it seems a narrow one, result in a cross pattern in the beam?

No it looked like a normal beam with a round hotspot.

Interesting. Which particular TIR did you use?

I’m not sure I can reveal my source. It’s a trade secret :stuck_out_tongue:

I bought the cheapest one on AliExpress for $0.75.
https://www.aliexpress.com/item/32817065402.html?spm=a2g0s.9042311.0.0.664e4c4dVSeFiB

I gave the DC fix a try today. Too close, and it doesn’t diffuse well. Too far and it doesn’t catch the warm light. It needs a reflector. I made a 13mm high reflector for it, but the light from the E21 is so concentrated it was still too close. Drr. I’m not sure if I will continue the project, since the E21 hates 2amps anyway.

I tested with all different powers on this new thread: