Re: Monitor calibration best practices
Re: Monitor calibration best practices
- Subject: Re: Monitor calibration best practices
- From: Marco Ugolini <email@hidden>
- Date: Tue, 14 Oct 2008 19:24:09 -0700
- Thread-topic: Monitor calibration best practices
In a message dated 10/14/08 6:21 PM, Roger Breton wrote:
> 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?
Hi Roger.
Yes -- or at least that's how I understand it.
> But suppose an LCD monitor with useful separate RGB controls. Then what?
There are many LCD displays out there that offer OSD controls for the R, G
and B signals. I'm not sure how they work -- possibly a pixel-level filter
that regulates the amount of backlight passing through?
However these controls on R, G and B signals work, they end up acting in a
way similar to gain in CRTs. Since these OSD "gain" controls -- however they
are achieved -- are completely independent of the CPU's LUT, I would think
that, in themselves, they do not cause any loss of levels on screen.
> 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.
Yes, I would tend to think so too. Change the white point using the
display's OSD "gain" adjustment sliders while calibrating with a colorimeter
using your preferred profiling software, and the subsequent profile will not
have to do any work aimed at establishing the desired color temperature. The
resulting profile's vcgt curves ought to be rather "linear" and only
minimally "wavy".
Marco Ugolini
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