Re: Questions on some basic definitions and concepts.
Re: Questions on some basic definitions and concepts.
- Subject: Re: Questions on some basic definitions and concepts.
- From: dpascale <email@hidden>
- Date: Mon, 10 Mar 2014 11:58:16 -0400
Hello Joseph,
Here are answers which try to supplement the ones already given.
D55 as daylight:
D55 is not the only reference to "Daylight". Any illuminant with a "D"
followed by a number, such as D50, D52, D65, D93, or D100, is daylight. The
one you use depends on application; generic graphic arts applications
usually select D50 while commercial paint applications are more D65. D55 is
often seen as a reference for flash photography. The exact "daylight" (or
even another Illuminant such as Illuminant-A) to use for a given application
will usually be specified in a standard (such as ISO 3664, ISO 12646, etc)
Note 1: The Standard Observer (2-degree or 10-degree) can also be different
between applications, but this is just another variable....
Color model, space, system, etc:
There is overlap, confusion and some distinctions that can be made in these
terms. Pantone and Munsell are often referred as "systems" (Munsell Color
System, Pantone Matching System) while RGB and CMYK (any flavour) are most
often referred to as "color spaces", but sometimes also as "color systems".
However, only RGB, CMYK and Munsell are color spaces, which can be specified
in terms of coordinates. Pantone is more of a color collection, in this case
as a series of colors which can be obtained by a mix of basic colorants. A
further distinction is that Munsell is an absolute color space, like L*a*b*,
XYZ, xyY, which can describe any color. This is not true of most RGB and
CMYK spaces (and certainly not Pantone). The fact that L*a*b* equivalents of
Munsell can be derived does not mean that they are the same space, but since
both spaces are absolute, you can always find corresponding values.
Note 2: Munsell equivalents of very saturated colors, near the chromaticity
diagram periphery, are estimates at best and have not been thoroughly
verified.
Note 3: L*a*b* equivalents of Munsell colors will be different for different
Illuminant/Standard Observer combinations.
Note 4: Historically the Munsell system was "renotated" (i.e smoothed) in
association with xyY coordinates under Illuminant C. The two systems remain
distinct.
12 bit vs 14 bit color space:
In principle there should be no differences in the gamut and 3D shape of
these spaces (if generated with the same camera and software of course).
There may be differences in smoothness within the space. However, I doubt
that any 3D color space visualization tool will enable you to see
differences, unless the data processing is not well done.
Danny
Danny Pascale
www.babelcolor.com
----- Original Message -----
From: "Joseph Chamberlain" <email@hidden>
To: <email@hidden>
Sent: Monday, March 10, 2014 7:41 AM
Subject: Questions on some basic definitions and concepts.
Hi again, everyone.
I have done quite a bit of research but haven't found the answer to two
questions. Any help or guidance you can provide will be very appreciated.
Here they are:
1. A textbook with a chapter on color theory (the book itself is not about
color technology) has a reference for daylight but I haven't been able to
find the source for this reference. Here it is:
" A full-spectrum light source, as recommended, is one with a color
temperature close to 5500 K (D55) that is specifically balanced throughout
the visible spectrum. This light source is defined as equivalent to
daylight in Washington D.C. (Bureau of Standards) in the month of June,
during the hours of 12:00 noon to 1:00 pm, when there is a slightly
overcast sky; the CRI of this light source should be 90 or higher. "
Do any of you know the source for this reference ?
2. I have been trying to understand the difference between a color model
and a color space but haven't found any text or any source that provides a
good definition for either one or explains both in a manner that is clear
and simple to understand. I am trying to understand the following:
2.a. Is Lab a color model or a color space ?
2.b. Is the Munsell Color system a color model ? In this case is the Lab a
color space based on the Munsell color system (color model) ?
2.c. Is RGB a color space ?
2.d. How can I draw graphs comparing the color spaces defined by RGB,
Adobe RGB and ProColor ? In case I have a raw file created by a 12-bit and
another created by a 14-bit camera, how can I draw a graph depicting the
difference in the color spaces of these two cameras ?
Thank you again in advance for your help.
Joseph.
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden