RE: Monitor calibration best practices
RE: Monitor calibration best practices
- Subject: RE: Monitor calibration best practices
- From: Roger Breton <email@hidden>
- Date: Tue, 14 Oct 2008 21:21:39 -0400
It may seem silly but I have to admit that I finally understand what is
meant by 'backlight' -- thank's CD.
Of course, all LCD monitors have Contrast/Crightness controls otherwise
dubbed "backlight" control on this List.
These Contrast/Brightness controls are not be considered as "true" separate
hardware Contrast/Brightness controls, the way we found them in the days of
CRTs but they nevertheless control, at the hardware level, just how much
light is being emitted (radiated) by the monitor.
Quantization now seems a little clearer in this context.
Please correct me if I am wrong but as long as one dims down the monitor
through the OSD's Brightness/Contrast controls, otherwise called the
"Backlight" in geek color management parlance, one is not losing discrete
brightness levels to quantization. Only when one is dimming one or any
combination of the three channels in the host computer video LUT, there are
quantization issues. Right?
That's why many regular contributors on this List advocate never changing
the white point control of an LCD monitor, right? For fear of introducing
quantization or loss of discrete brightness levels at the video LUT levels.
But suppose an LCD monitor with useful separate RGB controls. Then what?
I'll say *if* the white point adjustment can be controlled in hardware,
suppose from native 9000K down to 5000K or D50, then I think it is fair to
say that no quantization should ensue as a consequence. Other than the
slight quantization that would be introduced by calibrating the individual
channels to obtain a gray ramp (R=G=B=from 0 to 255) to the chosen white
point chromaticities (Little x/y). There I think it is unavoidable to have
some slight quantization being introduced as a consequence of calibrating
the grayscale from the monitor white down through the black point.
The only time that we should be freed from the specter of quantization is
when the grayscale calibration is carried inside the monitor LUT itself, as
with the Eizo's, the NEC's, the HP and the Quatto's, leaving the computer
video LUT untouched (linear).
Is that better?
Roger
> Yes, of course I meant lowering the display's brightness using the
> display's
> own controls, separate from the LUT in the CPU's graphic card.
>
> Marco
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