[argyllcms] Re: Spotread with x-rite DTP20 - low reading result values

  • From: Diego Carra <twwcar@xxxxxxxxxxx>
  • To: Argyll list <argyllcms@xxxxxxxxxxxxx>
  • Date: Sun, 5 Jul 2015 09:56:26 +0200


Chart printing:

Because the DTP20 measures exact distances using the markings on its ruler,
it's critical that the chart be printed out exactly the right size. If the
chart gets re-sized at all in the process of printing it, the DTP20 is
likely to fail in reading it. If you have a problem with this, you might
want to increase the page margins using the printtarg -m parameter, or
find a printing path that preserves the test chart size correctly.

I think it is difficult to read without a ruler. I have a Colormunki and i ve
made a selfmade ruled but it is difficult in any way to use it

Date: Fri, 3 Jul 2015 23:18:06 +0200
Subject: [argyllcms] Spotread with x-rite DTP20 - low reading result values
From: mmaterski@xxxxxxxxx
To: argyllcms@xxxxxxxxxxxxx

Hello all,

I'm Mike and I just've joined the list. Greetings from Poland.

Recently I bought a DTP20 of a Polish online auction website. It's just the
device and USB cable, no Pathfinder. The device have 'Xerox' written on it, so
I guess it came bundled with a hi-end printer. I wonder if those devices came
with no Pathfinder because I saw quite many online auctions with just device,
w/o Pathfinder.

I installed Argyll on my Windows 7 with no problems. I played around with few
commands, then decided to try spotread. When I measure a white patch (I tried
regular blank paper, photo paper and white background on a cover of magazine)
the biggest lightness I get is well below 50.

E.g. white background on a magazine cover:
Spectrum from 400.000000 to 700.000000 nm in 31 steps
11.789, 10.770, 9.439, 6.821, 6.424, 13.370, 19.580, 17.108,
12.348, 8.371, 6.259, 10.001, 14.670, 16.373, 15.940, 12.509,
9.143, 9.000, 11.002, 15.735, 18.994, 14.328, 8.203, 6.311,
7.962, 16.168, 22.266, 15.882, 7.553, 5.420, 7.398

Result is XYZ: 12.090000 12.610000 10.320000, LCh: 42.169637 0.541391
CCT = 5023K (Delta E 5.404917)
Closest Planckian temperature = 4897K (Delta E 4.600478)
Closest Daylight temperature = 4996K (Delta E 1.067160)
Color Rendering Index (Ra) = 95.6

It's the first spectrometer I'm using, but the measurement results seem low.
Magenta, yellow and cyan patches measured give rather dark colors too. I have
several questions:
I haven't printed any charts yet. I'm afraid I won't be able to make proper ICC
profile given the spotread results. Am I right?Is it normal for uncalibrated
DTP20 to give such low lightness values? The battery was charged at 50% to 75%
when I was doing the tests and the light source emits the light. But maybe the
light source is weak due to it's age or frequent use?Can I do anything to
improve the results? Is there a way to calibrate the device w/o Pathfinder?Is
this device worth anything w/o Pathfinder? I bought it for <70usd and it'd be
nice if I could use it with decent or at least ok results (home use, nothing
proffessional). But if not, I think I'll return it. The seller specified it can
be returned within 14 days.Please let me know what do You think. Any experience
with that or similar device? Big thanks in advance.

Best regards,

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