POV-Ray : Newsgroups : povray.advanced-users : Sunlight in Lightsys IV Server Time
18 Apr 2024 02:06:21 EDT (-0400)
  Sunlight in Lightsys IV (Message 1 to 2 of 2)  
From: Cousin Ricky
Subject: Sunlight in Lightsys IV
Date: 1 Oct 2016 22:11:29
Message: <57f06cd1$1@news.povray.org>
I just plotted the spectral curve for ES_Sunlight (filtered sunlight) 
from espd_lightsys.inc and compared it to figure 3 at:
   https://www.newport.com/t/introduction-to-solar-radiation

The curves are similar in shape, but the Lightsys curve is higher in the 
red region, while the Newport curve is highest in the blue and green 
regions.  What would account for the difference?

Newport.com's curve is for the Sun at zenith.  What was Pedro Aphalo's 
source?  Could Pedro's curve have been measured with the Sun at a lower 
angle?


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From: Cousin Ricky
Subject: Re: Sunlight in Lightsys IV
Date: 14 Oct 2016 07:15:00
Message: <web.5800bdceabfe701e87fca9f40@news.povray.org>
Cousin Ricky <ric### [at] yahoocom> wrote:
> I just plotted the spectral curve for ES_Sunlight (filtered sunlight)
> from espd_lightsys.inc and compared it to figure 3 at:
>    https://www.newport.com/t/introduction-to-solar-radiation
>
> The curves are similar in shape, but the Lightsys curve is higher in the
> red region, while the Newport curve is highest in the blue and green
> regions.  What would account for the difference?
>
> Newport.com's curve is for the Sun at zenith.  What was Pedro Aphalo's
> source?  Could Pedro's curve have been measured with the Sun at a lower
> angle?

I just compared the derived color of ES_Sunlight with actual sunlight reflected
off a sheet of white paper less than an hour after sunrise (more than 5 air
masses by my estimate), and the derived color was considerably more orange.
Assuming my monitor is halfway decently calibrated, the ES_Sunlight measurements
must have been taken through some serious air mass.


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