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: Joseph Chamberlain <email@hidden>
- Date: Sun, 23 Mar 2014 20:30:49 -0700
Danny,
Thank you for your help and the detailed nature of your reply.
Just to clarify, I was under the impression that the Munsell system was a color model.
When you say that Munsell, Lab, XYZ and xyY are absolute color spaces, I was aware of it. I was under the impression that Lab, XYZ and xyY were color models and Munsell a color system. Is this not the case ? In other words my impression was that color models were defined by mathematical formulas while color spaces provided different implementations of these color models. Based on your explanation my interpretation was wrong. Is this the case ?
Thank you again,
Joseph.
On March 10, 2014, at 8:58 AM, dpascale <email@hidden> wrote:
> 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.
>>
>
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