[argyllcms] Re: problems hitting white point (color temperature, RGB gain/contrast) while maintaining brightness: dE not stable

  • From: David Heinrich <dh003i@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 10 Dec 2009 11:27:26 -0500

This is really crazy, but this is what I guess I'm going to end up having to
do when adjusting the CRT: I put a spreadsheet window with 2 columns to the
right of the patch window and after each change, type in ~50 readings, get
an average, standard deviation, minimum, and maximum and compare to the
prior setting. Nuts, but its the best I can do:

Here's an example:
B-
1.2
0.2
0.3
0.6
1
1.6
2.1
1.3
1.1
1.6
0.9
1.7
1
1.4
0.7
1.4
0.1
2
0.4
1.3
1.6
0.6
1
0.5
0.9
0.6
0.5
1.5
0.8
1.6
0.1
0.7
0.3
1.3
0.3
0.3
0.8
0.4
0.2
1.9
0.4
0.3
1.5
0.3
0.2
1.2
1.3
0.7
0.4
1.1
avg 0.9
min 0.1
max 2.1
sd 0.6


On Thu, Dec 10, 2009 at 10:05 AM, David Heinrich <dh003i@xxxxxxxxx> wrote:

> > So even with the CRT in Standard Mode, doing fine-adjustments I still
>> can't
>> > get too great. The problem is still similar to what I quoted in the
>> original
>> > e-mail: when adjusting R, G, and B channel gains individually, the dE's
>> > bounce around as does the recommendation of which values to change.
>>
>> David, did You try to lover Your target brightness by 2-3 cd/m^2? If one
>> or
>> more channel gain levers are at their maximums, it may help.
>> This is a typical problem for some displays. There may be rather large
>> steps of
>> per-channel gain, so it's impossible to achieve the desired white point by
>>
>> hardware. With some displays I've got a best difference about 2.3dE or
>> even a
>> bit worse. The calibration can correct such deference.
>>
>
> Regarding lowering the target brightness, I presume I could just leave it
> the same but set one of the color gains to less than its maximum (90, 80?)
> and that wouldn't be any worse than changing the target as far as the
> accuracy of white and black points, right? But regarding this, I would think
> that the increments would be larger absolute values when channels are in
> their lower ranges rather than upper ranges; i.e., 99 is only 1% lower than
> 100, but 1 is 50% lower than 2?
>
> My final CRT settings are as such:
>
> STANDARD MODE
> =============
> Contrast 100
> Brightness 48
> R bright 98
> G bright 75
> B bright 100
> R contrast 100
> G contrast 60
> B contrast 58
>
> When adjusting my CRT, I can press the increase or decrease button and
> there seems to be some unmarked change in the values (i.e., I press up 1
> time, it might not change from 48 to 49..but if I press it twice, it goes
> from 48 to 49. I wonder if these "adjustments" that don't show a number
> change are actually doing anything?
>
> Now, it seems like the best my display can do is better than 2.3dE, around
> 0.2 or even = to sometimes 1.5 or 2. The problem is that my readings are
> bouncing around as far as dE's go. When adjusting RGB gains, readings
> fluctuate from 0.5-2 even when I'm not adjusting anything. So can the
> calibration still correct this? Wouldn't it need steady readings?
>
>
>>
>> > Is there
>> > a way to change how long the Spyder2 takes readings before updating? It
>> > would seem that if there was a way to get the program to average the
>> results
>> > of 5-10 updates or 5-10 seconds (I'm not sure how this works: is argyll
>> > getting a reading from spyder2 every several seconds, or is it averaging
>> the
>> > readings of spyder2 over several seconds?), it would smooth out this
>> stuff
>> > and allow for me to get a better idea as to what to do on my display.
>>
>> I'm just changing one channel by one step, waiting 5 seconds and looking
>> is the
>> difference less or more. Then I'm tuning the next channel. Repeat.
>> Sometimes I didn't see at the dispcal recommendations at all.
>>
>
> I'll try this out. After getting the dE below 3-5, maybe this is the best
> way, since what dispcal recommends bounces around so much.
>



-- 
Social sciences can never use experience to verify their statements --
Ludwig von Mises

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