Re: Sunlight
Re: Sunlight
- Subject: Re: Sunlight
- From: Roger Breton <email@hidden>
- Date: Sun, 18 Nov 2007 16:28:50 -0500
Hi Bertho,
> It would be very interesting to see the match if you had open the window to
> avoid the UV absorption of the glass but I guess it is getting cold outside
> in Canada by now.
Yes, well, I did find the courage to step outdoors in spite of the cold
(close to 32F, still not too cold) to repeat the measurement without UV
absoption. Like I said in my previous post, I did not find any significan
difference. Maybe it's because I don't use a correct geometric
configuration? The Spectrocam is not used a cosine corrector to measure in a
true hemispheric geometry but through an indirect technique whereby a first
contact measurement is made of a given surface (I use white ceramic tile)
and then, the head of the instrument is backed off, a few inches away from
the measuring surface and it takes what I think is the subraction of two
spectra, the first one and now the one with the ambient light. So I'm not
sure whether this technique is proper for the measuring I'm trying to do?
Some color scientist tell me that it's fine.
> A quick look at the data it looks like the error is getting a bigger and
> bigger in percent, the shorter the wavelength except that dip in the D50.
Right. It could be a calibration issue in the instrument?
> In other words, if you make a plot showing the % error between the two
> curves as % I think you will see the UV fall off.
I see your point.
> Where is the D50 from?
In the Spectrocam software itself, there is a function to dump the most
popular 'CIE Curves' in MS-Excel through the clipboard -- works very well.
That's where my D50 spectrum comes from. But, now that you mention it, I'm
going to check this data for conformance.
> I am surprised it is so "rough" but I have not
> looked at any D50 data for a very long time.
> Bertho
Thank's Bertho.
Roger Breton
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| | >RE: Sunlight (From: "Bertho Boman" <email@hidden>) |