[filmscanners] RE: CRTs vs LCDs

["Nuno Sebastião" <sebastiao@gmx.net>]

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk] On Behalf Of Dave King
Sent: sábado, 19 de Janeiro de 2002 4:16
To: SEBASTIAO@GMX.NET
Subject: [filmscanners] Re: CRTs vs LCDs


Dave King <kingphoto@mindspring.com>, wrote:

>>I'm assuming you researched the CRT situation before buying the Sony 
>>GMD-F520.  Do you know if it has individually adjustable guns?

Julian Vrieslander <julianv@mindspring.com> wrote:

>Yes.  Individually adjustable gain and bias for each gun.

I was thinking further about this today and realized I don't know what
the bias adjustment does.  Many monitors only have gain controls, and so
now I'm wondering how bias is different than gain, how it's used during
calibration, and the advantages (?) for color critical work. Thanks,
Dave

Well, tech speaking about gain and bias:
Say, you have an input X on monitor
Your output will be Y = mX + b.
Where m is the gain and b the bias aka offset.

So what you see on screen (Y) is the signal (X) that comes from video
card multiplied by gain (m) and added with b (offset or bias).
In a perfect monitor you would have something like m= 1 and b = 0 so
that the signal displayed by monitor is the same as the one that comes
from the video card. But as monitors age they need to be recalibrated to
show the desired signal so the need for the gain and bias.

Hope I was clear and helped,
Nuno Sebastião

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