D65 vs D50 reflection and transparency viewers
D65 vs D50 reflection and transparency viewers
- Subject: D65 vs D50 reflection and transparency viewers
- From: Henk Gianotten <email@hidden>
- Date: Sat, 27 May 2006 21:22:57 +0200
At 14:52 27-5-2006 -0400, Roger Breton wrote:
Incidently, speaking of viewers for graphic arts, has anyone found that the
GTI booths and the GTI fluorescent lamps never hit the 5000K mark when
measured (EyeOnePro and BabelColor in ambiant mode)? I'd be wiling to
compare notes with anyone on this List as I have personally measured many,
many such GTI booths over the last 16 months or so, at printers sites and
"institutions" like GATF, and I must say that I have never gotten better
than 4650k to 4800K out GTIs -- tops. Close to 5000K, granted, but never
quite the 5000K CIE u' v' chromatiticies called for in the ISO-3664:200x
standard, and, according to my measurement, almost always on the border of
the 0.005 tolerance CCT radius, if not flat outside. Which baffles me.
Arguably, it's possible many of those printers and sites all happened to
have worn out lamps the day I made my measurements. That would undoubdetly
affect the results, I don't debate it.
Roger,
I did some test on a new Heidelberg luminaire (Speedmaster 40 inch).
Exactly 5000 K.
Measured with a Minolta device.
Next to this press was a 9 month old Speedmaster 29 inch.
The temperature was around 4600 degrees. On the same Minolta.
We cleaned the glass panel and the aluminium reflector of this luminaire
and the temperature was back at 5000 Kelvin!
The UGRA strips (works like the GATF Rhem Strip) was identical on each
luminaire.
It seems that the dust in this plant reduced the blue content of the light.
The air filters were also filled with dust. But in spite of that, the panels
and reflectors were dusty.
Just some textile tissues and some anti-static cleaner will do the job.
How simple!
Regards,
Henk
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