R9 and red perception in SST40 and SFT40 6500K

LED Flashlights – General Info
1

I looked at two low CRI lights, the Sofirns IF19 (SST40) and HS21 (SFT40) and how they render colours of common objects. They both seem to lack red, but IF19 seems to show red better.

So to check if I’m not hallucinating, I looked at CRI measurements (both from @zeroair’s reviews of these two, from Moon to Turbo).

IF19
Ra: 68,66,66,66,67
R9: -45,-34,-32,-34,-31

SC21
Ra: 73,76,72,71,71
R9: -13,-3,-17,-16,-13

The IF19 is worst on both counts but I see the opposite - it’s not a huge difference. Am I hallucinating or the difference in those two CRI indicators is not that big on their scales?

2

With such pathological spectra the R9 values are pretty much irrelevant, and what influences your perception would depend much more on tint. Having lots of blue and orange can create the illusion of red.

3

I wonder what LEDs used in throwers would be better in the colour rendering department?

4

Also, I was under the impression that these two LEDs, SST40 and SFT40, differ mostly by doming not by phosphor. Why different CRI? Or maybe there are not that different - I don’t know how to translate the difference in Ra/R9 scores to what’s perceivable.

5

There is necessarily a difference in phosphor composition between domed and domeless LEDs. Dedoming makes the light warmer and typically pinker, so the phosphor mix must be adjusted to compensate in order to achieve the same target CCT and tint.

Ra score measures how close a given spectrum is to a blackbody spectrum of the same CCT, and can be checked by comparing against such a source, such as incandescent light or sunlight. R9 is harder to perceive. For LEDs, low R9 scores (say up to 50) typically indicate a lack of deep red. For scores in the 50-100 range, however, it is unclear whether the imperfect score is from too little red or too much red. Dedoming a 519A can drag the R9 down to <80 as it introduces too much red.

For throwers, even Cree lower-CCT 75CRI emitters, such as XPL-HI, offer a substantial, visually obvious improvement in color rendering over the 6500K emitters. Some variants may even measure close to 80CRI. If you wish to prioritize CRI over absolute performance, SFT40 3000K is a great warm option; for cooler options, dedomed 519A and FFL351A are great.

1 Thank