Re: Question: Measuring Delta E from two different spectrophotometers
Re: Question: Measuring Delta E from two different spectrophotometers
- Subject: Re: Question: Measuring Delta E from two different spectrophotometers
- From: <email@hidden>
- Date: Fri, 25 Aug 2006 15:20:32 -0400
Richard,
Are you saying the added fluorescent effect of the Xenon
bulb could skew the Colordata...
Yes...
results toward a closer measurement relative
to the standard?
... and no. Removing the fluorescence from the Datacolor
"could" bring the data closer to the BYK LED instrument
measurements.
And then sticking
the UV filter on the device would settle down the
fluorescence and yield a reading more similar to ours?
Yes, just a hunch, especially if it is a bright orange.
Keep us posted!
Danny
email@hidden
www.BabelColor.com
On Fri, 25 Aug 2006 13:45:33 -0500
Richard Brackin <email@hidden> wrote:
Thanks for the information.
That clears things up quite a bit.
I'll see about the UV filter on the Datacolor ... it's
at another lab.
I'll make that suggestion.
Are you saying the added fluorescent effect of the Xenon
bulb could skew the Colordata results toward a closer
measurement relative to the standard? And then sticking
the UV filter on the device would settle down the
fluorescence and yield a reading more similar to ours?
regards
Richard
email@hidden wrote:
Hello Richard,
I have seen the exact same phenomenon when measuring
yellow, orange
and red BCRA tiles with five different instruments
(including a NIST
traceable one). Some instruments gave errors in the 7-8
DeltaE range
(CIELAB) relative to the NIST traceable measurements,
while others
were in the less than 1 DeltaE range.
All these colors have very sharp cut-off slopes, and
this spectral
characteristic makes the mesured color very sensitive to
small
spectrometer wavelength calibration shifts.
First, get away from CIELAB. You will measure smaller,
by a factor of
two plus, and more realistic, compared to visual
assessment, color
differences using CIE94 or CIEDE2000. Still, you
probably will not
achieve the less than 1 DeltaE target.
You may want to look at an inter-instrument calibration
solution, such
as netprofiler from GMB, but this one in particular may
not be
compatible with the instruments you have.
I have also done inter-instruments matching on my own,
using from 8 to
30 samples, and have improved matching in all cases (a
factor of two
improvement is not uncommon).
The Xenon vs LED may also be the cause of the problem
since the Xenon
is likely to generate more fluorescence. Can you try a
UV filter on
the Datacolor?
Danny Pascale
email@hidden
www.BabelColor.com
On Fri, 25 Aug 2006 12:40:21 -0500
Richard Brackin <email@hidden> wrote:
We have supplied identical (or as close as it can get)
color
standards to some manufacturers.
We are all measuring L*a*b* values of a series of films
against those
standards, (Green, Blue, Red, Purple, Gray, and Orange,
etc.).
We, as well as their color laboratories, are taking
measurements on
these very specific pigmented colors and we're all using
different
measuring devices.
In discussing the issue with the head of color matching
at one lab,
we are seeing similar (not extremely close, but similar)
L*a*b*
measurements for the standard.
However, we're all seeing color variances of approx 1
delta E on all
of the colors except this particular orange.
While they are seeing 1 delta E comparing the orange to
the standard,
we're seeing 13 delta E.
We're measuring Delta E (CIE 1976) D50 at 10 degrees.
(CIE 1994 Graphics shows approx 6 delta E but we've been
asked to use
CIE 1976).
What are some factors that would make one color show up
so differently?
Should we be using a different color model for
measurement?
The standard probably has a variance of 0.5 delta E
across the surface.
They are using DataColor SF600 Plus and we're using
BYK-Gardner
ColorGuide Sphere.
The Data Color uses Xenon, the ColorGuide uses LED.
Could the pigments used to make their orange color cause
such a
drastic difference in measurement between the two light
sources?
many thanks
Richard
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