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

  • From: Michał Materski <mmaterski@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 3 Jul 2015 23:18:06 +0200

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,
12.348, 8.371, 6.259, 10.001, 14.670, 16.373, 15.940,
9.143, 9.000, 11.002, 15.735, 18.994, 14.328, 8.203,
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:

1. 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?
2. 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?
3. Can I do anything to improve the results? Is there a way to calibrate
the device w/o Pathfinder?
4. 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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