[argyllcms] Re: Best settings ?

On Friday 25 July 2008 08:46:50 pm Olivier Marchetta wrote:
> Hal, my LCD is a E2403WS and it has 1000:1 contrast too.
>
> What setting am I missing to get the best ratio ? Should I lower the
> brightness/contrast from the OSD menu ?

One of the issues with LCDs is that none of the controls are in any way 
standardized.  So what adjustments I did with my Samsung 225BW will likely not 
be meaningfull for another brand or even perhaps another model.  I spent a lot 
of time playing with each control and doing measurements to get a handle on 
what the controls actually did and how they interacted with each other.

For example I found on my monitor that the RGB controls didn't really change 
the white point.  Rather these altered the gray point (and to some extent the 
black point) which no profiling/calibration package is setup to measure as 
part of guiding the user to set these controls.  These appeared to be more 
like gamma controls for the individual RGB channels.  I also found that other 
controls like the brightness control and contrast control would actually 
affect the white point in fairly significant ways.  So it took a lot of 
testing and tweaking to get the white point close to 6500K and the gray point 
close to 6500K while at the same time having a reasonable contrast ratio and 
over all gamma.  In other words there is no simple formula or technique or 
recipe that I can give you for how to set your LCD controls.

CRTs on the other hand typically have more controls for this sort of thing and 
the controls are highly standarized although some CRTs will have more control 
options than others.  For example I have a Dell P1130 which is really an OEM 
Sony G520.  This has controls to set the white point (on some monitors will be 
labeled as the R, G, B contrast controls), black point* (usually labled as R, 
G and B brightness controls), white level (contrast control) and black level 
(brightness control).  These controls work just like they would on any other 
CRT with the same set of controls.  It would be a big service to users if the 
makers of LCDs would have the same level of control standardization but I 
don't expect to see this anytime soon.  

* Most inexpensive CRTs will not have a set of black point controls .  On my 
Dell CRT I have to use the Expert color mode to expose these controls.

> 2008/7/26 Olivier Marchetta <olivier.marchetta@xxxxxxxxx>
>
> >  Voici le résultat de dispcal -r -yl :
> >
> > Current calibration response:
> > Black level = 0.46 cd/m^2
> > White level = 134.22 cd/m^2
> > Aprox. gamma = 2.19
> > Contrast ratio = 293:1
> > White chromaticity coordinates 0.3168, 0.3263
> > White    Correlated Color Temperature = 6300K, DE to locus =  0.4
> > White Correlated Daylight Temperature = 6303K, DE to locus =  5.0
> > White        Visual Color Temperature = 6313K, DE to locus =  0.4
> > White     Visual Daylight Temperature = 6489K, DE to locus =  4.8
> >
> > So yes it is 0.46 and not 46 :)
> >
> > But I think my spyder is not very accurate, data will vary from 0.46 to
> > 0.48 and other settings too from one to another test.
> >
> > Olivier,
> > 2008/7/26 Hal V. Engel <hvengel@xxxxxxxxxxx>
> >
> >   > So 47 cd/m^2 is actually a light gray on my system. Are you sure this
> >>
> >> is not 0.47 cd/m^2? That would still be a liitle on the light side but
> >> not too out of line. >That would give a contrast ratio of about 298 to
> >> 1. Where as my LCD has a constrast ratio of about 917 to 1. The
> >> advertised static contrast ratio of my >LCD is 1000 to 1.

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