[argyllcms] Re: How do I measure individual patches on my display?
- From: Leonard Evens <len@xxxxxxxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 07 Mar 2009 10:27:59 -0600
On Sun, 2009-03-08 at 00:51 +1100, Graeme Gill wrote:
> Leonard Evens wrote:
> > I've created a gray scale in gimp of 11 successive squares going from
> > pure black (0,0,0) to pure white (255,255,255) going up in equal
> > increments.
> >
> > I want to read the values on my display as seen by my Eye-One-Pro. I am
> > trying to use spotread , but I apparently don't understand what I'm
> > doing.
> >
> > Problems:
> > 1. I use -N, but it still insists of calibration.
>
> There may be a couple of bugs have crept into this option.
>
> > 2. It asks me about FWA, which I don't understand. I skipped that and
> > just pressed a key to get XYZ and Lab readings. But the readings don't
> > seem to make sense. In particular the L readings don't decrease
> > consistently from white to black. I've tried -d, -db, and -e.
>
> -d should do it. What sort of readings do you get ?
I just tried it again with the -d and -yl options but left out -N. This
time the L readings seemed to make sense. I list them below. The only
other change I made was to make the squares larger on the screen.
Looking at the Eye-One-Pro, I see there could be a problem if the source
patch doesn't entirely fill the outer circle of the weighted frame that
the instrument is held in as it rests on the monitor. (If that is the
source of my problem, I may have to do my calibration/profiling over
again since I used the -p .7,.5,.6 option in order to keep the sample
patch outside the window that the monitor controls put on the screen.
I'm not sure .6 is large enough to be sure no extraneous light is
getting to the sensor.)
There is still one thing I don't understand. I thought L was supposed
to range from 0 to 100. My highest reading was over 105.
I attach a text file L.txt with the L output readings. The scale was
displayed in gimp, with the sensor fixed and the scale shifted from one
square to another between readings. The scale was in grayscale mode in
gimp and the input values are those shown by gimp. I also attach the
complete set of readings vals.txt.
>
> Graeme Gill.
>
>
Square Input Output
10 255 105.860670
9 230 93.940370
8 204 85.879957
7 178 78.645224
6 153 69.437998
5 128 57.806120
4 102 47.759576
3 76 37.723172
2 51 27.804883
1 26 6.162737
0 0 2.873259
10 Result is XYZ: 112.830705 115.935574 119.380536, D50 Lab: 105.860670
1.632665 -16.120469
9 Result is XYZ: 84.741068 85.132938 88.182815, D50 Lab: 93.940370 5.056700
-14.946493
8 Result is XYZ: 67.530377 67.747347 69.482265, D50 Lab: 85.879957 4.893998
-13.225587
7 Result is XYZ: 54.342756 54.315295 55.556650, D50 Lab: 78.645224 5.057350
-12.129206
6 Result is XYZ: 39.971952 39.955744 41.267167, D50 Lab: 69.437998 4.552952
-11.461645
5 Result is XYZ: 25.799400 25.757468 26.948776, D50 Lab: 57.806120 4.064208
-10.493090
4 Result is XYZ: 16.521956 16.605896 17.202723, D50 Lab: 47.759576 2.890589
-8.672592
3 Result is XYZ: 9.938519 9.933699 10.134302, D50 Lab: 37.723172 2.869103
-6.798514
2 Result is XYZ: 5.244963 5.385098 5.477363, D50 Lab: 27.804883 0.636068
-5.462228
1 Result is XYZ: 0.657940 0.682250 0.699159, D50 Lab: 6.162737 0.004637
-2.574673
0 Result is XYZ: 0.318814 0.318086 0.447033, D50 Lab: 2.873259 0.489230
-3.486065
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