On Tue, 22 Jul 2008 19:13:38 +0100, Orchid XP v8 wrote:

>>> OK, that's just absurd. The sofa and the rug are *exactly* the same
>>> colour. How the hell can the machine tell them apart? Additionally,
>>> how on earth can it tell what colour they were originally? That's
>>> impossible...
>> 
>> Except it clearly isn't impossible, because it was done.
> 
> Well yeah, OK, I rephrase: It defies explanation.

See my explanation below. :-)

>> Adjusting the white
>> balance of the photo involves picking out something that actually
>> is/was white (like the white on the baby's shirt).  That gives the
>> computer a reference to make the adjustments from.  When photos age,
>> they tend to age consistently and the colours adjust with consistency. 
>> The computer basically is doing an "undo" on the age effect applied by
>> real life.
> 
> But surely no scanner on Earth has sufficient resolution that you can
> amplify a signal by many orders of magnitude and not be swamped by
> noise? The photo posted contains almost no blue whatsoever, so you'd
> have to apply a ridiculous amount of gain to that channel...

Except that's clearly not the case.  There is blue in the photo, though - 
that's clearly visible by looking at a breakdown of the RGB channels 
using something like the GIMP.  There's certainly more red and green in 
the photo, but just look at the outfit the baby's wearing and tell me 
there's no blue there - on the shoulders and the matching "pants" (don't 
know the word for that part of the outfit).  Along the baseboard to the 
left of the chair - that's a purplish colour there, blue is a component 
of that.

Jim

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