[argyllcms] Re: Question regarding White Point and spotread
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 05 Nov 2014 08:47:09 +1100
robert@xxxxxxxxxxxxxxxxxx wrote:
Really, that is a whole lot of help to me when I haven't a bog's notion what
the 'perfect diffuse reflector' is, or how it relates to me trying to
measure a spot color.
<http://en.wikipedia.org/wiki/Diffuser_(optics)>
You're measuring reflectance. So naturally that is the amount
of light reflected from something. The most light that can
be reflected for a diffuse measurement (0/45 or 45/0 degree geometry)
is 100%. Since the meadia is what is part of the unknnown
being instruments are setup to measure relfectance with 100%
scale being 100% reflectance.
Relative means that it is with reference to the actual paper color.
What does that mean?
100% scale being the reflectance of the paper.
My understanding is that in relative, white is the
paper white.
Yes.
So the profile will shift colors from the working space white
(??) towards the paper white, whereas Abscol does not.
I don't know what you mean by "working space". These are reflectances
that are converted to XYZ values as if it they illuminated by
a D50 illuminant. A chromatic adapation is used to map the paper
value to the white point.
So if we are going
from D65 to a yellowish paper, Abscol will print everything with a blue
tint.
No problem ... but if you don't cut off previous posts then the latest post
has a record of all the follow-up to the original question.
Everyone on the list has the previous emails, and the list archive
is abailable as well.
Graeme Gill.
Other related posts:
