Re: i1Pro weirdness & fix
Re: i1Pro weirdness & fix
- Subject: Re: i1Pro weirdness & fix
- From: dpascale <email@hidden>
- Date: Mon, 29 Feb 2016 11:07:47 -0500
Hello Ernst,
I have a license of Patchtool but did not know this restore function.
It is not hidden but not obvious... (perhaps too much so!)
It was placed in this "Info" dialog because this is where it was expected a
user would go if there was a calibration issue.
Such a check could be done at every calibration but I think that many users
would feel uneasy by being asked for an impromptu lamp restore.
Now for whiter than white measurements...
There are three aspects to this question:
1- The intrinsic instrument precision. The instrument is not perfectly
accurate and a certain amount of absolute and inter-instrument agreement
errors should be expected. This is not visible when you are below L*=99 but
it becomes obvious at L*=100.
2- The "heating" effect. As noted by Graeme and others, repeating
measurements at short intervals may show an increase in measured L*. I have
seen this effect for quite some time; my first souvenirs are around the time
I manufactured "pure white" targets, i.e. near 100% reflection, where this
effect is most noticed (and maybe more so for the older i1Pro). To control
this effect when measuring fluorescence (as in the CT&A Fluorescence tool),
I have been recommending a VERY METHODICAL procedure, waiting for instance
20 to 30 seconds between each measurement.
(See for the AN-8 app note in this page
http://www.babelcolor.com/tutorials.htm for more info)
Note: I initially tought of an optical coupling interaction between the lamp
and the optical fiber within the i1Pro but the Halogen cycle mentioned by
Graeme makes a lot of sense.
3- Teflon is a strange material, not so much in terms of molecular
composition but how its structure (and thus the manufacturing process)
affects reflection. It has mentioned in the scientific litterature that
certain forms of Teflon could be seen with more than 100% reflection, an
effect attributed to a lensing effect of the sub-surface structure.
Danny
www.babelcolor.com
----- Original Message -----
From: "Ernst Dinkla" <email@hidden>
To: "Graeme Gill" <email@hidden>
Cc: "ColorSync" <email@hidden>
Sent: Monday, February 29, 2016 9:13 AM
Subject: Re: i1Pro weirdness & fix
I had a gut feeling my i1 Pro (UV enabled) is reading too much reflectance
on whites now. I measured a new paper for SpectrumViz recently, the Arca
Proline Vibrant Superior Rag etc, that showed the highest white
reflectance
of any paper so far. I know it comes from Felix Schoeller and I have
similar papers from that stable that measure a bit lower in reflectance.
Platine category. There has been a steady improvement in inkjet coatings
whites over the years though. I got more alarmed when I measured a
plumber's Teflon tape stack of 5mm thick and the reflectance gave a Lab L
100.+ where 9mm thicker stacks in the past did not go beyond L 99. I see
no
sign of fluorescence in the Teflon. This will not be the same piece of
Teflon tape I used before but I do not expect beyond 100 numbers in any of
them.
I have a license of Patchtool but did not know this restore function.
Checked whatever could be wrong in my calibration of the i1 Pro,
calibrated
then and used the restore function of Patchtool. It soon gave the feedback
that no restore was needed, if should be fine. I still measure Lab L 100.3
on that Teflon, climbing to 100.5 on a fresh tape layer. Tested the i1 Pro
on some 3mm thick color acrylate samples I have stored. The new i1 Pro got
initiated on them in 2010 when it arrived and I stored the mesurements
with
the samples. Differences at most 0.3 (black) on the Lab L values of the 7
samples where I see 0.2 between measurements today. About 0.4 (0.7-0.1) in
time on the a b values.
Conclusion: Nothing to worry about. This must be a very bright Teflon tape
sample and the i1Pro (UV enabled) is somewhat optimistic near Lab L 100 +
minute content of OBA in the Teflon, Lab b -0.1 in more than half the
measurements. Lab L 94 of the white acrylic sample is unaffected . The i1
Pro calibration white spot is fixed at Lab L 95.7. If it had aged and get
darker the white acrylic sample measurements should have showed that, no
change in the Lab L value though. The Lab b shifted 0.7 though either in
the calibration spot or the acrylic sample or both. I should have made
spectral plots of the two or three calibration whites here six years ago,
not just Lab numbers written down.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2016 update, 700+ inkjet media white spectral plots
On Tue, Feb 23, 2016 at 2:13 AM, Graeme Gill <email@hidden>
wrote:
Alexey Gribunin wrote:
> By the way, just as an idea - is it possible to make special "cleaning"
utility for i1Pro
> and Spectrolino, which will turn lamp on forcibly for some seconds to
"clean" it?
Looks like X-Rite beat me to that -
someone pointed out that there is a function exposed in BabelColor
PatchTool
called "lamp restore" that appears to use a new function in the i1Pro SDK
(V4.2.2 or
later). See
<http://www.babelcolor.com/index_htm_files/PatchTool_Help.pdf>
page 87.
This sounds a lot like it is intended to deal with what I discovered.
[ From my own limited experience with my instruments, I'm wondering if
i1Pro2's
are more prone to it ? ]
It's possibly too that a recent copy of X-Rite's i1Diagnostics also
includes such
a function, although it doesn't seem obvious what or if it is doing this
kind
of thing.
I'll add an option to ArgyllCMS spotread to diagnose and attempt to fix
this
problem in i1Pro's as well, and be a bit more up-front about what's going
on.
Graeme Gill.
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