[argyllcms] Re: Dispcal on WinXPSP2+ i1pro

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 29 Oct 2007 14:29:01 +1100

Roger Breton wrote:
I am not sure I successfully completed the calibration of my LCD display
with V0.70 dispcal since, towards patch 60 of 100, in the verification pass,
I got a nice "dispcal.exe has encountered a problem and needs to close"
run-time error?

See below. It sounds like two copies of dispwin were started.
One ran, the other aborted. I've not run it on WinXP (I
don't have a WinXP test system at the moment), so It's
not clear how two copies of the software were started.

Do you think you might have done this accidentally ?

And got:

Setting up the instrument
Instrument Type:   Eye-One Pro
Serial Number:     102242

So far so good. Now, what I don't understand is why did the program went
through a second round of instrument calibration below?

Seems like a second instance of dispcal was being run.

Setting up the instrument
Instrument Type:   Eye-One Pro

Was it the result of some of the arguments I used on my command-line?

Shouldn't be.

Display adjustment menu:

Press 1 .. 7
1) Black level (CRT: Brightness)
3) White level (CRT: Contrast, LCD: Brightness)
4) Black point (R,G,B, Offset)
5) Check all
6) Continue on to calibration
7) Exit

Here, I admit I didn't quite knew what I was doing when I pressed "5". What
confused me was the text in bracket for each choice. For example, for Black
level, I wasn't sure what this test would do for an LCD display, since it
showed CRT: Brightness in bracket. I guess what you mean to say, in bracket,
is "for a CRT monitor this relates to the Brightness knob".

Yes, the information in brackets is the control the adjustment
relates to.

> When I take the
time to read through your reported measurements things start to make sense
however. Maybe a better term for brightness would be Luminance? Because
that's the units into which dispcal is reporting brightness?

That's not what the controls are labelled though, so that would
be very confusing for users. On a CRT, the "Brightness" control
is the one that has the greatest influence on black level.
LCD's don't have any direct controls for black level, so
(naturally), there's no effective way of adjusting this.

That's little to do with dispcal, and a lot to do with
the display technology, and what the user is going to
ask it to do.

Doing verify pass with 100 sample points
patch 100 of 100
Verification results:
Brightness error = -1.507341 cd/m^2
White point error = 0.241024 deltaE
Maximum neutral error (@ 0.314318) = 66.765037 deltaE
Average neutral error = 5.135653 deltaE

Hmm. It's usual for the verification to indicate a worse
result than the last calibration pass, but I've never
seen anything like this. it's way off. Perhaps
this is a result of two copies of the program running
at the same time, and overlapping/competing ?

Graeme Gill.

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