Re: Understanding color balancing
Re: Understanding color balancing
- Subject: Re: Understanding color balancing
- From: Dennis Dunbar <email@hidden>
- Date: Tue, 20 Dec 2005 11:00:32 -0800
Hmmmm.... I don't think color correcting has to be like Rocket Surgery. This
approach seems waaay too complicated.
Without converting from one color space to another ie RGB-L*a*b-RGB the best
way to do color corrections I've found is to use 2 Curves adjustment layers.
One layer is set to luminance blending and the other is set to color. Then
tone, contrast, color and saturation are all able to be adjusted separately
without messing up the other.
For what Lars wants to do I would suggest using a similar model, the color
only Curves layer would allow him to do the corrections he wants.
The biggest question I have is why would it be necessary to create a new
tool for this when the tools we have are very capable. It just takes a
little time practicing with them to learn how to use them.
Dennis Dunbar
The Digital Transformer
On 12/19/05 10:20 PM, "email@hidden"
<email@hidden> wrote:
> Well, I'm no expert in this particular aspect (ie. I haven't had
> sufficient experience in actually making things that do this), but
> your guts are probably wrong. It seems to be generally accepted that
> black point adjustment (for instance), is best performed in a linear
> light space (ie. XYZ, or RGB without the gamma etc.), because this
> mimics the actual physical processes that create different black points
> (haze etc.) The accepted means of adjusting white points is to use a
> Chromatic Adaptation transform. If you are not familiar with this,
> it involves starting in XYZ space, converting to a cone sharpened
> space via a 3x3 matrix, adjusting the white point (a simple linear
> process, known as the "Von Kries" method), and then transforming
> back to XYZ space. Typically the sharpened cone space uses the
> "Bradford" matrix. This all mimics the processes that occur
> in our eyes, where our individual color sensors adjust their
> "gain", independently of each other. (Googling for some of these
> terms should return more information. There are a number of books
> that introduce basic color science out there too).
>
> As for mid tones, I'm not too sure. One could justify either a process
> in a linear light space, or in a L*a*b* type color space (that will
> preserve the neutral axis), depending on what underlying process you
> think is being corrected for. (Perhaps all three adjustments
> can be done in the Bradford space ?) Or try a number of these
> approaches, and see what works best. [That's actually what makes
> developing new stuff hard - exploring all the dead ends,
> until you end up with what works.]
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