What should be the correct distance of OPPLE Lightmaster to the light source when measuring CCT and XY ?

LED Flashlights – General Info
1

We all know that when measuring dB SPL or sound level, the distance from sound source to sound level meter is always 1 Meter. Is there a standard distance for light meters, color meter and spectrophotometers from the light source?

I asked because CCT and dUV varies depending on the meter to light source distance. It seems that when you are putting the Lightmaster closer to the light source, you get higher CCT reading and more positive dUV reading. The longer the distance of the OPPLE lightmaster to the light source, the lower is the CCT reading and dUV reading (lower or more negative)

2

What should be the correct distance

that varies based on how bright the output is set… the meter will max out at 50,000 lux, so when that happens we have to either move the light farther away, or reduce the output.

I try to test at an output and distance that produces about 20,000 lux on the meter, but at low outputs that is not possible

Interesting observation… I just did a test at two different distances (2" and 4") and the results do differ slightly (the light is at 50 lumens):

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The test at higher Lux increased the CCT by 24K and the DUV went lower by 0.0002

CCT and DUV also varies by output, this is the same single LED light, at two different outputs:

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Also note that LEDS are not identical. Individual LEDs vary in CCT and DUV. For example here are two different lights both with the same type of LED:

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In this example the CCT was pretty close, but you can see there is a bigger difference in the DUV when comparing different LED samples

So, dont expect exact accuracy when measuring LEDs, there are a lot of variables that affect the results…

3

My data on 98 CRI LED, note that i use the same LED, same setup, forward voltage, current etc. the only difference is distance from LED to OPPLE Lightmaster

TEST1
|5540lx|7372K|X=0.3020 Y=0.3107|dUV= -0.0007|
|3164lx|7124K|X=0.3051 Y=0.3128|dUV= -0.0013|

As you can see, the closer the OPPLE lightmaster to the LED @5540lx, the higher the reading of both CCT and DUV 7372K and -0.0007. When you move away the OPPLE Lightmaster, the brightness drops to 3164lx and also the CCT drops to 7124K and dUV drops to -0.0013.

4

7100K CRI98 from a single LED?

The Opple has an extremely low wavelength resolution and can only be used to vaguely guess common LED types.

5

it’s one of those 6500K violet pumped ultra high CRI LED. My other samples is 7300K. they came in one reel from a friend, i don’t know if all the LEDs in the same reel are 6500-7400K.

6

wondering which version of Opple, 3 or 4?

the cct change was just 3%
the duv change was just duv 0.0005

the only difference is distance

if you are testing a bare LED, changing distance changes which part of the beam reaches the sensor…

the results can be different depending which part of the beam is being measured:
aFRu13v

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a pebbled Tir could be used to blend the output to be more consistent accross the beam

7

i’m using OPPLE 3. i tried it on a CREE COB and Linear LED fluorescent lamp which is housed in a diffused white housing, i got the same result. The closer the OPPLE to the light source, the higher the CCT and DUV reading. So I guess, the higher the LUX reading, the higher the CCT and DUV reading.

8

I believe that depends on the type of LED. for example:

Opple 3 data, only distance changed.

  1. Novatac light (reflector), Nichia 3000K 219b at 9.3 Lumens:

lux 5212
cct 3207, duv -0.0002

lux 11075
cct 3176, duv -0.0010

cct went down and duv went down as lux went up

  1. SC21 Pro light w Pebbled Tir and DeDomed 519a 4500K at 10.9 Lumens:

lux 2868
cct 3492, duv -0.0024

lux 7092
cct 3495, duv -0.0026

cct went up, duv went down as lux went up

  1. Novatac (reflector) Cool white low cri LED at 8.1 Lumens:

lux 3773
cct 6433, duv 0.0036

lux 7288
cct 6741, duv 0.0049

cct went up, duv went up as lux went up

note there is also fluctuation of the Opple reading, even when the light is not moved… iow, the LED is changing its cct and duv without changing distance.