Viewer Metamerism
Viewer Metamerism
- Subject: Viewer Metamerism
- From: Ray Maxwell <email@hidden>
- Date: Tue, 04 Sep 2007 10:38:47 -0700
This has been a great discussion about metamerism. However, I want to
expand the discussion a little.
Many years ago I put together a test pattern. I was not the first and I
think that this pattern is a standard in the industry. It consisted of
a background printed with a 50% black. On this background was printed a
matrix of squares that used a mix of Cyan, Magenta, and Yellow that was
very close to gray. The matrix contained no black. It was knocked out.
All of the squares contained the same amount of Cyan. Going across
the sheet was a 1% variation of the magenta tint. Going down the sheet
was a 1% variation of yellow.
I had this sheet in a D50 viewing booth in the hall of the company I
used to work for. A friend of mine that I worked with named Gordon
Pritchard came down the hall. Gordon was our commercial printing expert
and had been in the industry for many years when he joined our company.
I asked him to pick the square that matched the gray of the background.
He picked a square. I told him that he and I must see "eye to eye"
since it was he same square that I had picked. He said, "That is the
correct square. How could you choose another." I then told him that I
had used the $10,000 spectrophotometer and compared the CIELab values.
It showed that the square up one and left one was a better match. He
immediately replied, "The instrument is wrong". I then saw two women
walking down the hall. I asked one two turn her back and then asked the
other to pick a matching square. She chose a square above the one that
the instrument had shown was the best match. I then asked the second
woman to pick a match. She chose a square to the left of the other
women. I then asked Gordon what he made of that. He said that it was
an epiphany.
I have read studies that say that viewer metamerism can be as large as a
delta E of five.
I worked in the area of color science. I was asked to set up the first
few beta test programs for our first half-tone laser proofers. When I
came into a company, I always asked for the "golden eyes" of the company
who was going to sign off and accept the new proofer. I then brought
out the above mentioned test pattern and asked which was the best
match. I then knew the bias from the "standard observer" that I needed
to account for when setting up the proofer. It always varied from
customer to customer.
Given this experience, I have always tried to get the industry to adopt
colormeteric standards based on the CIE standard observer. It might not
be exactly what a given person likes, but it would be consistent across
the industry.
Has anyone else done this experiment? Be careful when you run the
experiment. You must not let any subject of the test see what the
previous person has selected. It has a very strong bias and can effect
the person's selection.
Ray
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