Interesting Munsell colors experiment
Interesting Munsell colors experiment
- Subject: Interesting Munsell colors experiment
- From: Roger Breton <email@hidden>
- Date: Sun, 22 Jun 2008 12:08:22 -0400
Dear color folks,
Just a little word to tell you that I've added a new file to my .Mac web
site called "MunsellValue6.zip", to be found here:
http://homepage.mac.com/graxx/FileSharing4.html
It's a "pet" project I'm doing around a set of Munsell color book I acquired
last year on eBay. The file in question was put together using Adobe
IllustratorCS2 on the Mac but it should opens fine under Windows as well.
To fully appreciate the value of this document you should be familiar with
Layers, since, half of the layers won't be visible at the moment you open
the document.
What is being shown here is a selection of Munsell colors at Value 6.
For those not too familiar with the Munsell system, there are three
parameters to describe a color in the Munsell system, hue [H], value [V] and
chroma [C], given the notation abbreviated HVC. CIE Lab was largely based on
Munsell color space.
You will find the document contains all 10 primary Munsell hues and their
corresponding possible chromas levels.
In the Illustrator document I created, the selected colors are represented
by color circles plotted on an CIE ab diagram (a*/b*). There is an L* scale
at the right of the diagram but I did not care to use it since all colors
would have plotted more or less one one top of the other.
There is a layer for each Munsell hues (5R, 5YR, ...).
Hidden, is also a series of layers showing what happened to the colors once
processed through an ICC profile and printed on an Epson 4000 printer.
I have not calculated deltaEs between the original and the actual but the
distance represented by the black arrows should give a clue abut the color
difference; the longer the arrow, obviously, the larger the color
difference.
As you'll see, some colors are better matched than others. This is where it
gets interesting -- for me, at least.
I did not anything fancy or special. I used some Epson Dupont proofing media
I happened to have a box of, for this experiment. I'm not too crazy about
that media but at the price I picked it up on eBay, it was OK. I used some
kind of CMYK printing RIP to drive the printer. All measurements were made
with a Spectrocam -- always like using that instrument. It's well supported
by MonacoProfiler so that's what I used to create the profile. Since I did
not want to measure all night I only used a basic set of 378 patches.
The Munsell color measurements were made using a SpectroEye (could have used
the Spectrocam?). And then transferred in D50/2CIE Lab in Adobe
InDesignCS2. So that's where the printing document originated. I exported
that document to PDF with no color conversions, so colors remained in Lab
all the way to the printer (late binding) and were only converted to the
printer ICC profile inside the printing RIP, using absolute colorimetric
intent.
I measured all colors on the printout, with the Spectrocam, and proceeded to
plot the results in that Adobe Illustrator CS2 document which I just posted.
As you can see, not all colors are matched accurately.
I expect things to improve using a larger color sample (IT8.7/4 or higher)
and using some other media (less optically brightened, especially). So
that's probably what I'm going to do next, to see what's going to happen
with those arrows. In principles, they should shorten in length.
Now, the whole reason I embarked in this experiment in the first place was
to test the correspondance between simulated colors and the visual system.
This is the essence of metamerism, folks. Since I have all these real
Munsell color chips at my disposal, it's easy to tell how good is the
simulation or, put another way, whether my visual sensation agrees with the
colorimetric measurement.
Roger Breton
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