Does daylight CRI change w/TOD like CT?

[aznsx]

Most are aware of the change in CT (color temperature) of 'daylight' over a range with change in TOD (time of day) and sunlight's angle of incidence through the atmosphere.

Many / most tend to refer to 'daylight' as being a reference value of '100' CRI.

Question: Does 'daylight' CRI, as measured with appropriate instrumentation, change through a certain range as a function of TOD or that angle as CT does, or is it really a fixed reference value regardless of the change which affects measured CT?

Thanks!

Edit: Focused title, and added overstrike.

 

[KITROBASKIN]

Didn't the people who came up with the CRI measurement use an incandescent? (Black body?) for the reference is what I remember.

 

[aznsx]

Didn't the people who came up with the CRI measurement use an incandescent? (Black body?) for the reference is what I remember.

Good question, and another one I can't answer, but while certainly related to my question it's also outside of my intended / stated scope; which remains fixed on relevance to Earth daylight - per this premise I suggested:

Many / most tend to refer to 'daylight' as being a reference value of '100' CRI.

Do you believe that premise is in fact incorrect? If so, perhaps my question is invalid?? (which it may well be)

EDIT: Perhaps daylight is not actually '100'. If so, I'd still like to know if it changes throughout the day, as CT does.

I think I just worded that poorly. My question is not at all dependent on the validity of that premise, and that was essentially an unnecessary distraction from my question I guess.

 

[JustAnOldFashionedLEDGuy]

For >5000, CRI = 100 refers to a very specific spectrum similar to noon day sun, cloudless sky. Most of the time, sunlight is not 100 CRI.

 

[aznsx]

For >5000, CRI = 100 refers to a very specific spectrum similar to noon day sun, cloudless sky. Most of the time, sunlight is not 100 CRI.

Thank you Sir. Now all I need to do is develop a CRI correction/derating factor based on delta-CT away from solar noon value, and I'm in business!!

Just joking! I do appreciate your post though - no joking about that!

 

[JustAnOldFashionedLEDGuy]

<5000K, we use the spectrum of a black body radiator.

One thing critical to remember, CRI is a reference, it is not a true measure of quality. 5000K, 4000K, even 3000K and 2700K black body radiators that are bright don't exist in nature so we couldn't really adapt to them.