Plotting CIE charts

m

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Feb 27, 2008, 2:34:26 AM2/27/08

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Is there an Excel add-on to plot CIE charts?
If not, any stand-alone software?

Thanks,

-Martin

Roger Breton

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Feb 28, 2008, 1:29:47 AM2/28/08

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Timo could answer this better than I can (www.aim-dtp.net) but if you use xy
scatterplots and some tricks in the order in which you place the data in
subsequent rows, it's possible to plot things like a*b* gamut projections.
It's possible to plot individual a*b* coordinates too using this technique.
But I understand that may not prove very sophisticated. At least this is
free.

Roger Breton

Gernot Hoffmann

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Feb 28, 2008, 5:55:13 PM2/28/08

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m schrieb:

What is a CIE chart ?

Best regards --Gernot Hoffmann

Douglas G. Cummins

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Feb 28, 2008, 6:07:05 PM2/28/08

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I've just done it myself. You can get the data at http://www.cvrl.org/
and make your own xy scatter plot in Excel.

--
Douglas Cummins
Calcoast - ITL

Douglas G. Cummins

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Feb 28, 2008, 6:08:38 PM2/28/08

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Umm.... you're kidding, right?

--

PTKen

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Feb 28, 2008, 6:48:43 PM2/28/08

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I'm pretty sure he is referring to a chromaticity diagram. Of course,
my assumption could be wrong. You are correct to point out that
calling it a CIE chart is incorrect and a bad habit to get into!

Ken

Timo Autiokari

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Feb 28, 2008, 10:35:29 PM2/28/08

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What Gernot asked was perfectly a valid question. I have also been
thinking what are CIE charts and in addition to that what does it mean
to plot them.

Timo Autiokari

Douglas G. Cummins

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Feb 29, 2008, 1:25:27 AM2/29/08

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The term CIE chart is commonplace albeit not complete. The particular
color space should be referenced at the same time - e.g. plotting color
on a CIE 1931 (2° observer) chart.

I do not see Gernot pointing out that calling "it" a CIE chart is
incorrect. I only see him asking, "What is a CIE chart?" Hence my
remark. Shame on Gernot as a long-time contributor to this group for
not expanding on his extremely short question/comment.

A chromaticity diagram is only the "Horseshoe" plot of the color space,
often with the colors in the background. If you're interested in
plotting colors within the color space, then you've gone beyond the
chromaticity diagram.

Please remember that color science is not limited to just trying to
match color output from various devices (e.g. monitor & printer), which
is what most of the participants in this group debate about. It also
includes testing the color of real world objects to make sure they fall
within an established tolerance, possibly under different illumination
conditions. Using charts is a fast and simple means of doing this.

If people still can not envision what it means to plot color on a CIE
chart, I'll be glad to show some examples.

--

m

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Feb 29, 2008, 2:44:03 AM2/29/08

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> What is a CIE chart ?

CIE 1931 xy Chromaticity Diagram

...did I really need to say that or are you just having fun at my
expense?

Did anyone not understand what I am asking? My apologies if it was
confusing.

-Martin

Gernot Hoffmann

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Feb 29, 2008, 6:36:03 AM2/29/08

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The OP could have explained his application, therefore
my question.

We encounter 'CIE charts' as illustrations

http://www.fho-emden.de/~hoffmann/ciegraph17052004.pdf

or as diagrams for measured or calculated values:

http://www.fho-emden.de/~hoffmann/colcalc03022006.pdf

Both systems are based on PostScript instead of Excel.

Best regards --Gernot Hoffmann

m

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Mar 1, 2008, 1:06:48 AM3/1/08

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> We encounter 'CIE charts' as illustrations

> or as diagrams for measured or calculated values:

> Both systems are based on PostScript instead of Excel.

Yes on all of the above. I am looking for tools --of any kind-- to
plot these sorts of diagrams.
One project is to plot LED xy measurements in the context of various
gamut triangles.
A different project is to compare gamut triangles.
Both for illustrative (to publish a document or include in a
powerpoint) and analytical purposes.

Thanks,

-Martin

PTKen

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Mar 1, 2008, 6:36:21 AM3/1/08

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On Feb 28, 8:25 pm, "Douglas G. Cummins"
<Douglas.Cumm...@MAPSONcalcoast-itl.com> wrote:

> A chromaticity diagram is only the "Horseshoe" plot of the color space,
> often with the colors in the background. If you're interested in
> plotting colors within the color space, then you've gone beyond the
> chromaticity diagram.

I don't think that's correct. It's called a chromaticity diagram
because you are plotting the chromaticities--usually the x-y
coordinates--of the color. The lightness information is lost on this
diagram since it's a projection. The "Horseshoe" is a plot of the
chromaticities of the spectrum locus. "Plotting colors within the
space" is simply the showing the chromaticities of other colors. Why
is that going beyond the chromaticity diagram? That's actually what
it's intended to be used for.

Oh, and although you see it all the time, it's often recommended to
"not" show colors in the background of a chromaticity diagram because
1) no inks or display can reproduce the full gamut 2) the lightness
dimension is not represented and 3) there is no means to include
colors like black, gray, and brown.

Ken Fleisher

Timo Autiokari

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Mar 1, 2008, 4:26:52 PM3/1/08

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m wrote:
> I am looking for tools --of any kind-- to plot these sorts
> of diagrams. One project is to plot LED xy measurements in
> the context of various gamut triangles. A different project
> is to compare gamut triangles.

Please take a look at my free AIM-XLA Exel add-in:
http://www.aim-dtp.net/aim/technology/aim_xla/index.htm
With it you can easily do all the above and a horseload more. There are
about 200 functions and command all together, some patience is required
in the familiarization phase. And you do need to dig in to the help
file, not just browse it.

Timo Autiokari

m

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Mar 3, 2008, 3:50:28 AM3/3/08

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> Please take a look at my free AIM-XLA Exel add-in:http://www.aim-dtp.net/aim/technology/aim_xla/index.htm
> With it you can easily do all the above and a horseload more. There are
> about 200 functions and command all together, some patience is required
> in the familiarization phase. And you do need to dig in to the help
> file, not just browse it.
>
> Timo Autiokari

Thanks, I will.

-Martin

Douglas G. Cummins

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Mar 3, 2008, 7:17:57 PM3/3/08

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PTKen wrote:
> On Feb 28, 8:25 pm, "Douglas G. Cummins"
> <Douglas.Cumm...@MAPSONcalcoast-itl.com> wrote:
>
>> A chromaticity diagram is only the "Horseshoe" plot of the color space,
>> often with the colors in the background. If you're interested in
>> plotting colors within the color space, then you've gone beyond the
>> chromaticity diagram.
>
> I don't think that's correct. It's called a chromaticity diagram
> because you are plotting the chromaticities--usually the x-y
> coordinates--of the color. The lightness information is lost on this
> diagram since it's a projection. The "Horseshoe" is a plot of the
> chromaticities of the spectrum locus. "Plotting colors within the
> space" is simply the showing the chromaticities of other colors. Why
> is that going beyond the chromaticity diagram? That's actually what
> it's intended to be used for.
>

It ain't a diagram if you're plotting on it. It's then a chart or a plot.

'nuff said.

PTKen

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Mar 4, 2008, 12:40:09 PM3/4/08

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I suppose we have different definitions of what a diagram is.
According to Wikipedia (which is not always a reliable source, but I
don't disagree with this definition):

"A diagram is a 2D symbolic representation of information according to
some visualization technique. Sometimes, the technique uses a 3D
visualization which is then projected onto the 2D surface.

...

There are at least the following types of diagrams:

* Graph-based diagrams: ...

* Chart-like diagram techniques, which display a relationship
between two variables that take either discrete or a continuous ranges
of values; examples:
...
o scatter plot
..."

That sounds a lot like a chromaticity diagram to me--including plots
of 'any' color, not just the spectral colors.

If you have a different definition of a diagram, please share it.
Thanks.

Ken Fleisher

On Mar 3, 2:17 pm, "Douglas G. Cummins"

Douglas G. Cummins

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Mar 5, 2008, 1:50:44 AM3/5/08

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Really? You want to argue semantics? And then you go to a user-edited
encyclopedia rather than one of a plethora of online dictionaries? And
after all that your quoted definition does not contradict what I wrote.

You stated that calling a chromaticity diagram a CIE chart was incorrect
and a bad habit. That's nonsensical. A chart is a plot of data points
and if you're plotting a set of cartesian coordinates in a CIE color
space, then you've got a CIE chart. It's also a CIE chromaticity
*chart* or *plot* (since chromaticity and color mean just about the same
thing), but the *diagram* is a specific data set - not just any data plot.

see http://www.efg2.com/Lab/Graphics/Colors/Chromaticity.htm

I say that the CIE Chromaticity Diagram is the "horseshoe" of locus
points plotted on a x-y chart (dependent on CIE 1931, 1976, or whatever
standard observers you're using to plot) - often times the colors within
the loci are printed in the background. Once you start adding data
points to the diagram then it's a chart or plot and no longer just the
CIE Chromaticity Diagram.