Not everything, but an ANSI white chart should answer a few questions…
CCT goes lower left to upper right along the dotted line. Tint goes up and down along the more vertical lines. “Duv” is the distance from the dotted line. The shades most people prefer are below the dotted line between 4000K and 5000K.
The SST-20 4000K emitter this thread is about would fall into the 5A3 square, according to its official specs and the measurements it gets on turbo. However, at lower levels it shifts up and to the right, to about 5C4.
The “FA1” bin mentioned a couple comments ago is “5A1” on this chart. It might be a decent tint for SST-20, since at low levels it should only shift as far as 5D2. However, as far as I’m aware, no one on this site has ever acquired any in the FA1 bin. They don’t seem to exist. Most SST-20 around here are the 5B4 bin, which is roughly 5C3 at low levels.
Some time ago I owned two D4S, XP-L HI 3D 4000K and SST-20 4000K because I wanted to check which I prefer and leave just one for myself.
The throw was nearly the same, I had problems to determine which throws further.
But with both lit up at the same time, the SST-20 tint was obviously biassed with green. And I’d guess SST-20 boils up 20% sooner.
For these two reasons I sacrified high CRI for better tint and less heat. XP-L version is still with me.
(After all I still consider SST-20 to be a great LED. But similary to 219B - it just should not be pushed hard. A perfect diodes for keychain or other small lights)
+1. It may well be that, statistically, more people prefer rosy Duv to green Duv, and maybe even to perfect BBL. But there must be a significant, if silent, minority, that, for general usage, prefers no Duv. Just as, I guess, I find myself in what must be a significant minority of people who prioritze CRI over tint. My eyes can compensate for tint variations, but there is no way to compensate for low CRI.
I would be surprised, but this matches what the researchers found. There was always someone who complained, no matter which tint was used… so no single choice will please everyone. However, the tints which had the fewest complaints were rosy to a degree of approximately –10 to –15 mduv.
It may also relate to the old idiom about rose-colored glasses. The phrase didn’t come from nowhere. Humans, in general, seem to find a touch of pink to be a bit more pleasant. Meanwhile, the counter-idiom of jade-colored glasses (or being jaded) refers to a more unpleasant outlook.
The ones I see discussed most often are the Lee minus-green filters. For example:
Compared to super green LEDs like the FB4 SST rosy ones look much better to my eye. However if I have a neutral tint (FD2 SST 20 and my good tint lottery 219cs in my D4) I find I much prefer it to a particularly positive or negative DUV.
To me the SW45K looks great next to super green LEDs, but when I compare it to any emitter that’s remotely neutral it looks pretty bad (even if it ends up making me perceive all others as “green”). It’s offensively rosy in the same way some are offensively green. That’s just my experience anyway ¯\/¯ The FD2 is as close to perfect as I’ve seen so far.
But… WHY? If the Daylight Locus is more green than the BBL, what is the supposed advantage of “merging” them this way? To say it another way: What light source is anyone measuring that they’d want to skew the “results” in this way?
Are you seriously complaining about the color of daylight? The advantages are numerous for technical and non-technical reasons. We evolved under daylight. We want our lighting to agree with daylight. Not have some weird discrepancy.
I understand that our eyes are naturally matched to daylight. But, why merge the lines? What advantage is it in scientific testing of “fluorescent” lights, including LEDs? The two lines exist already, and can be measured against, so what does this add that we need?
EDIT: BTW, I’m not complaining about daylight. That would be silly!
