[ptx] Off-Topic: kelvin and red/blue balancing

[Pablo d'Angelo]

On Sun, 08 Feb 2004, Ed Halley wrote:

> 
> This is slightly off-topic for Hugin, but there seem to be a fair number
> of color-savvy mathematics folks who are on this list.
> 
> Dave Coffin has provided a file called dcraw.c which offers access to
> many camera "raw" formats.  It is a work of reverse-engineering in many
> cases, because manufacturers don't fully document each camera format.
> 
> To support conversion at its highest quality, dcraw.c needs to know the
> white balance parameters.  These are performed by multiplying red
> samples and blue samples by two multipliers.
> 
>     final[r] = sample[r] * factor[r]
>     final[g] = sample[g]
>     final[b] = sample[b] * factor[b]

Does that mean the the camera save the completely raw response from the ccd
or whatever optical sensor? In that case, for raw files one wouldn't have to
go to the great pain of estimating the cameras OCEF.. or could use a simpler
model for it...

But probably every camera manifactures saves slightly different data here,
and we can't rely on getting a linear ccd response from the raw data as
well.

ciao
  Pablo
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