Re: Colorsync-users Digest, Vol 4, Issue 449
Re: Colorsync-users Digest, Vol 4, Issue 449
- Subject: Re: Colorsync-users Digest, Vol 4, Issue 449
- From: tom lianza <email@hidden>
- Date: Tue, 11 Dec 2007 01:42:51 -0500
Hi Mark,
I'll try to answer your questions in order...but there really aren't
simple answers. Factors such as optical geometry and polarization often
have much bigger impact on measurement accuracy than any of the spectral
issues.
1. In the absence of that scientific instrument you are searching for in the X-Rite's basement, is it valid to
conclude from your comments that an instrument like the EyeOne Pro will provide a better spectral
description of a monitor and therefore a more accurate profile, all OTHER things being equal?
I don't think that you can make a general comment about a spectro being
better than a colorimeter in every instance. It depends highly on the
spectral structure of the source and the characteristics of the spectro
itself. It also is highly dependent upon what you are trying to
measure. Generally a colorimeter will measure into the darker regions
better than a spectro. A spectro can certainly measure dissimilar
sources with smaller differences relative to a reference
spectrophotometer, than a colorimeter. The biggest issue with a spectro
is the bandwidth of the device. A product like our i1 has a relatively
large bandwidth (I'm at home and don't have the spec in front of me so I
won't quote it) A great deal of effort is spent in the calibration of
the device characterizing the operating characteristics as it measures a
number of different references, both emissive and reflective. It is
still very difficult to get an i1 to match a minolta CS1000 or pr650
measurement on an arbitrary display. It is also difficult to get a
CS1000 and pr650 to match on every display. As the gamut of a display
starts to approach the spectral locus, the situation becomes very
tenuous. If I was measuring a wide dynamic range, wide gamut display, I
would personally pick a colorimeter. That colorimeter would be
calibrated by spectral reference device. If I was trying to get
displays of greatly different spectral characteristics to match (CRT to
LCD), I would probably want a spectro photometer. So as a
generalization, wide dynamic range, known emissive characteristics, ->
colorimeter. Smaller dynamic range, arbitrary spectra, ->
spectrophotometer.
2. Will the spectrophotometer always be a better instrument when comparing the spectral qualities of
different types of monitor - CRT, LCD, LED...
As I said above, if I was comparing devices or trying to calibrate
different technologies to the same aim, I would likely default to a
spectro. I would argue that things start to get very difficult when
trying to compare absolute measures of Yxy, particularly with the
shorter wavelength greens used in many wide gamut displays. On LED
displays, we have to consider that the center wavelengths change with
temperature. This is a real serious issue when comparing measurements
between instruments. You really do have to wait for 30 minutes to an
hour before doing any serious measurements of an LED output.
Regards,
Tom
Message: 1
Date: Sun, 09 Dec 2007 08:10:00 +1100
From: email@hidden
Subject: Re: LED displays: some comments and observations.
To: email@hidden
Message-ID: <email@hidden>
Content-Type: text/plain; charset=ISO-8859-1
Tom,
Just to recap... If I remember rightly the discussion about LEDs sprouted from the Samsung XL20 and the
possible discrepancy in profiling that may arise from using two different colorimeters - the Huey and the i!
Display. I reflect on the notion that gained currency recently (at least in some quarters) that colorimeters,
in general did a better job than a Spectrophotmeter when profiling monitors because of their 'tristimulus
architecture'. (Hope that doesn't sound like B. S. but without a technical background it's the best I can
do!).
1. In the absence of that scientific instrument you are searching for in the X-Rite's basement, is it valid to
conclude from your comments that an instrument like the EyeOne Pro will provide a better spectral
description of a monitor and therefore a more accurate profile, all OTHER things being equal?
2. Will the spectrophotometer always be a better instrument when comparing the spectral qualities of
different types of monitor - CRT, LCD, LED...
Mark Stegman
-
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