Re: was: Brightener in Epson Premium Glossy
Re: was: Brightener in Epson Premium Glossy
- Subject: Re: was: Brightener in Epson Premium Glossy
- From: "Adriano Von Markendorf" <email@hidden>
- Date: Tue, 1 Oct 2002 10:04:14 -0300
Dear Graeme,
>
In my experience, the issue of getting non-pure yellows when trying to
>
emulate a larger gamut with a smaller gamut device, is all about the
>
type of gamut mapping/clipping being used. Profiling packages that
>
use a simple geometric approach (mapping out of gamut colors towards
>
a central point for instance) often have this problem. Profiling
>
packages that map out of gamut colors towards the closest in-gamut
>
colors tend to have purer yellows.
I will check this information with the vendors.
>
> Could be better use a non-UV reader with a diferrent light source like
>
> spectrocam? they claim to get better espectral response (lees uv reading
and
>
> a little more wavelenght range) from your xenon light.
>
>
A lot of instruments use an incandescent light source similar in spectrum
>
to the standard "A" source. It is generally assumed that in Graphic Arts
>
that standard viewing conditions will be a daylight spectrum of D50 or
>
D65 color temperature. Many practical viewing conditions are actually
>
fluorescent simulators of D50 or D65, which in fact have a similar
>
white point but rather different spectrum.
>
>
The claim of an instrument like the spectrocam, is that their
>
xenon light source is more like the real viewing condition of D65.
Really? I will check this too. When I bought this instrument, the
techinical/sales-man (as usual) tell me that was D50. And I'm not sure if I
have this information described in my pack (The Avantes folks do not answer
to me any email- too bad).
>
If in fact you have a viewing booth with real D65 spectrum (I don't
>
know how this would be done economically, and it's hard to know when
>
real daylight is exactly at 6500K), then, yes, this should
>
help enormously in accounting for fluorescent whitener effects.
I think that could understand your point, but you mean that I have a light
source that It's NOT pratical or evem efficient for many reasons?
>
The problem is that most of the D65 viewing booths out there
>
aren't a real D65 spectrum, and could have quite a different
>
balance between their UV and non-UV illumination levels,
>
leading to a mismatch between the xenon instrument,
>
and the viewing booth.
So, the diference come up.
>
I've looked at the spectrum of a couple of fluorescent D50
>
viewing booths with tubes from different manufacturers, and while
>
the visible spectrum and white points were very similar, they had
>
quite noticeably different emissions in the UV wavelengths. Paper
>
with large amounts of fluorescent whitener in them, could therefore
>
be expected to look somewhat different in the two booths.
Well, I think that this phenomenon would be normal.... I only guessing.
Could you appoint what instruments did you test?
>
> I saw in the list comments about this capacity of abstract the uv
component
>
> from PM4.
>
>
It's not really clear exactly what PM4 does. I got the impression that
>
it was some sort of "rule of thumb" compensation for fluorescent whitener,
>
but it's hard to tell if that is all it is, or whether it is something
>
more sophisticated.
Their claim to have very sophisticated algorithimics to eliminate this
effect.
Thank you for the depply reply, but I have more doubts than before :-?
Best regards,
Adriano von Markendorf email@hidden
"I-C-Cm vitamin's inside" Rio de Janeiro - Brazil
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