High CRI (Warm white) 4 Sevens Preon 2 + Neutral White Comparison Review

UnknownVT

Flashlight Enthusiast
Joined
Dec 27, 2002
Messages
3,672
This is pretty subjective -
the cool white ought to be closest to daylight D65 - which is color temperature of 6500K - that is supposed to be noon daylight with clear blue skies - but I find it slightly blueish

Sunlight is supposed to be 5500K ("D55" if it exists - the closest standard is D50 @ 5000K)
the current batch of Neutral Whites seem warmer than D50 (I have CRI90 D50 fluorescent "Sunlight" tube to compare) - but the current Neutrals seem close enough that I actually on first sighting thought 4Sevens had sent me Cool White instead -
so in this batch (and I freely admit my bias) the current Neutral White seems closest to D50.
the Cool white definitely shows as too blue and the High CRI (warm) is definitely too amber/yellow.

If I have some time I'll take photos of these lights on white paper that's illuminated with D50 lighting.

I did both GE 5000K "Sunlight" CFL (Compact Fluorescent Light)
and GE 6500K "Daylight" CFL -

these bulbs may not have color temperatures accuracy to the least significant digit
- but are probably "good enough" for our comparison purposes -

Another note, if it means anything - both the CFL's have CRI=82
(but more than likely very different deviations from "perfect" to any of the LEDs)

Flashlights on paper illuminated with -
GE 5000K "Sunlight" CFL
5000K_HiCRI.jpg
5000K_WW.jpg


5000K_NW.jpg
5000K_CW.jpg


GE 6500K "Daylight" CFL
6500K_HiCRI.jpg
6500K_WW.jpg


6500K_NW.jpg
6500K_CW.jpg


These are good for seeing how the lights differ from reasonably well known standard color temperatures of 5000K (D50 - tiny bit warmer than "sunlight") and 6500K (D65 - "Daylight")
The exposures were auto as-is with Fixed Daylight White balance -
NO post processing adjustments for tint or color.

I then did some post processing to try to get the pictures to look like I saw them - the main problem was in balancing the flashlight hotspot (which was much brighter) to the surrounding areas illuminated by the CFLs.

Details I selected a grey point (should be neutral grey) near the lower left corner - the furthest point from the flashlight beam - so ought to be the CFL light only - then did minor adjustment to the brightness so they'd all look similar in brightness. Therefore there is some color/tint adjustment (but it is everything in the whole picture) due to the grey point selection - I was hoping that this would be an "idealized" way to see the pics, as the "white" paper is supposed to be tint/color free - as it was, I don't think I was that successful - but I present these without any further excuses -

5000K_HiCRI_adj.jpg
5000K_WW_adj.jpg


5000K_NW_adj.jpg
5000K_CW_adj.jpg
 

js82

Newly Enlightened
Joined
Jun 22, 2011
Messages
130
This is pretty subjective -
the cool white ought to be closest to daylight D65 - which is color temperature of 6500K - that is supposed to be noon daylight with clear blue skies - but I find it slightly blueish

Sunlight is supposed to be 5500K ("D55" if it exists - the closest standard is D50 @ 5000K)
the current batch of Neutral Whites seem warmer than D50 (I have CRI90 D50 fluorescent "Sunlight" tube to compare) - but the current Neutrals seem close enough that I actually on first sighting thought 4Sevens had sent me Cool White instead -
so in this batch (and I freely admit my bias) the current Neutral White seems closest to D50.
the Cool white definitely shows as too blue and the High CRI (warm) is definitely too amber/yellow.

If I have some time I'll take photos of these lights on white paper that's illuminated with D50 lighting.

In the meantime read these - please -

Most of us "see" common tungsten lighting as "white"
(even though a lot do know it is very yellow/amber when compared to sunlight/daylight).

There is a very good reason for this,
as our eyes/brain adjusts for what we perceive as "white" for different light levels,
please see:

Kruithof curve
- Wikipedia, the free encyclopedia


The Color of White

Those are very interesting articles. No wonder somebody on this forum said that their vision adjusts to the color temperature. So in fact it adjusts because of the total brightness level rather than just due to the overall color temperature.
 

bodhran

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Joined
Oct 18, 2008
Messages
437
Location
California
How true a color the camera shows I don't know, but to my eyes the HCRI and WW beam shots look identical. This isn't a complaint because I ordered a Mini CR123 for the tint as much as the CRI. I'm never without my warm CR2 and I think it does very well rendering colors, though doesn't compare to my HDS HCRI.
 

UnknownVT

Flashlight Enthusiast
Joined
Dec 27, 2002
Messages
3,672
I posted the below in another thread - but thought it may be appropriate to post it here:

CRI is not that simple to understand - and I claim no expertise in it -
However CRI is always in reference to a "black body" radiator of the same color temperature - so for a cool white or a white that approximates to sunlight - those would be compared to the "black body" of actual "Daylight" or "Sunlight" - this is not as easy as it sounds since those are nature and can easily vary from day to day and season to season - so the CIE has developed standard ("white") illuminant of D65 (normally called daylight at 6500K) and D50 (@ 5000K which is actually a shade warmer than noonday sun only (no sky) which is normally regarded as 5500K = D55 (actually also a CIE standard illuminant).

Artificial light - at one time the most prevalent household lighting was/is tungsten light - about 2700K - just from this color temperature alone one knows this has to be significantly warmer tint/color than daylight or sunlight.

However the BIG trick for CRI for artificial light - is the approx black body for tungsten lighting is actually the tungsten light itself - so by definition a tungsten light bulb has CRI=100.

Yet just about everybody knows that it is very hard if not impossible to read certain shades of yellow printing on white and really difficult to distinguish navy from black (try picking these socks in household lighting).

So what's the value/worth of CRI in this instance -
well we can say if a light renders color the same way or how much it deviates from a tungsten bulb....

OK....
is that worth anything?

In the case for medical type application - perhaps because traditional inspection lights have just about all been tungsten based - so a light that approximates to tungsten is "good" -

BUT think on this what if a light emphasized certain color like reds and orange - so that certain anomalies get highlighted/emphasized by the light may be better for that type of inspection - but since that would deviate from a tungsten light, the CRI by definition would be lower, and could actually be abysmal - yet I would think it may actually be more useful than a High CRI warm white that approximates to tungsten (to get the High CRI).

Take another rather silly example just to illustrate my point - - UV dye detection - we will not see these under and normal light even with high CRI - yet using UV rich light - like some blue LEDs will make these visible - so which light do we actually see the UV dyes better with - obviously the UV rich light - but these will have CRI probably in the single digits - ie: pretty awful CRI......

Ah! I hear you all argue this is a silly example and taking a specialized case -
As far as I know medical practice is specialized, being able to see skin/flesh anomalies is a specialized study - most of us lay-people do not go round looking for those, with or without flashlights - so if a flashlight was designed and wavelengths tuned to highlight or emphasize those anomalies - I would bet their CRI would not be that good.......
so much for High CRI -


So as far I am concerned CRI is just not too well understood -
we are also too enamored with numbers - a CRI=100 may not always be "perfect" -
if it were why can't we see yellow print on white
or pick navy from black under a light that is rated CRI=100?
 
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