[argyllcms] Re: Contrast vs Brightness on my LCD monitor and related questions

  • From: Leonard Evens <len@xxxxxxxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 07 Dec 2008 11:43:56 -0600

On Sat, 2008-12-06 at 23:23 +0100, Peter Karp wrote:
> Hi Leonard,
> > I still feel I am having difficulties because I don't understand hwo
> > to use Brightness and Contrast in the monitor controls.
> For a TFT it's mostly easy. Reet the contrast setting to the default
> value and never touch it again. This setting is totally nonsense and I
> still wonder what the engineers/companies are thinking when they use
> it on a flat screen display. Contrast setting on a CRT was a whole
> different story (setting the gain).

One thing that still puzzles me is just which of the 8 options I should
choose when using dispcal -v -o ...    I can use Brightness to set the
white level (option 3, I think), but what about black level (option 1).
I've been using various combinations of Contrast and Brightness to set
options 1 and 3.  Should I just ignore option 1?  The default settings
are Brightness 100, Contrast 75, but then when I shift to Custom mode,
the Contrast level drops to something lower, 60, I believe.  In any
case, the default luminance level is (visually) much to high.   I think
I prefer something in the range 100-120 cd/m^2. 

> Some better displays don't show you a contrast setting at all (Eizo,
> Quato - when digitally connected). That's the best way. Others (for
> example some NEC models) offer a contrast setting, but can be reset to
> the default values pretty easy. Some displays offer a contrast setting
> and it's not possible or unclear how to reset the complete OSD
> settings or a specific one alone. This is the worst case. If possible
> don't buy such a display.
> > Also, with the RGB monitor controls set at the default 50/100, I am
> > getting lower color temperatures than I would prefer. I will
> > experiment some more with the controls and also try setting the
> > color temperature.
> I don't know your specific model, but in general it's a very good idea
> to start from the default/factory values.
> 1) Don't touch contrast setting at all. (They use the monitor LUTs to
> mimic a CRT behavior which does not make sense and will lead to
> banding) -- so if available reset to the factory value.
> 2) Test if the brightness setting only influences the backlight --
> which it should. For this matter use some gray ramps and/or gradients
> (non colormanaged is the best for this purpose). You should not loose
> any levels, when altering the brightness. If it does, take care or
> better buy a better display which does not connect the monitor LUT to
> the brightness control.
> 3) If RGB default values leave headroom then test if increasing the
> RGB values will lead to banding in R, G, B, Gray ramps. If it does not
> you can use the complete range, if it does you have to reset the RGB
> values to the default value and wire those default values as the
> maximum _usable_ values to your brain ;-)
> 4) Use the brightness control to set desired luminance (or slightly
> higher, because you will loose some luminance when you use the RGB
> settings to reach the target whitepoint).
> 5) Then you can alter the color temperature (white point) with _two_
> of the RGB controls. Leave one of them -- depending on the choosen
> whitepoint -- at the maximum _usable_ setting. As a hint you can
> remember that lowering the green channel will also raise the measured
> value for the other two channels (on most displays).
> 6) Recheck the luminance if needed/wanted. Important: the visual
> appearance of the luminance (depending on the ambient light!) is much
> more important then to reach a specific measured value.
> Alternativ route when you want to buy a new display: look for a
> display which can be hardware-calibrated. For example used NEC 2180UX
> go pretty cheap and can be calibrated under OS X and Windows with some
> solutions.
> Hope this helps a bit.
> Regards
> PEter

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