Tony writes ...
> I think this debate does belong here. Very few people,
> including me, understand all this stuff fully,
> yet it inescapably goes with the territory of
> film scanning.
OK then ... but let's back up a bit, and agree on some concepts.
Color exists, and devices cannot capture all of it. For example, we
might begin with ignoring the quality of our lenses, and skip to
something we have day-to-day control over, and realize that certain
films are more-or-less sensitive to certain wavelengths. Do we want
to understand this as the film's gamut?? (Andrew feel free to jump in
... please!).
At this point in the discussion, I am at a loss to define the fixed
point around which all other definitions of color (color spaces,
device gamuts) are relative. I would love to believe this is the
CIELAB color space, but I've read there are different versions of Lab
color space. This is aggravating to me ... we need to first find that
"fixed" reference point. It also seems to me RGB must somehow be
"fixed", but there exists an anchor by which we define PS color
spaces. From here we'll be able to understand to what degree film can
capture nature ... a scanner can capture film ... the appropriatness
of our Photoshop working spaces.
I entered into this thread only to express an observation regarding
understanding RGB color space and the gamut associated with it (assume
any color space, but it began with the color spaces associated with
Photoshop ... e.g., AdobeRGB). My point was one of curiosity ... not
only are there colors (as defined by a RGB value) which are outside
the working space, there also exists colors as defined by RGB values
which do not exist at all. A question to ask here would be if anyone
believes, that when they defined the RGB editing color space, if they
didn't define it as such that the endpoints (the "pure" R,G & B
values) would never be actually found. That is, don't we define these
editing color spaces to ^enclose^ anything we may encounter???
I'd love to learn more from discussing this subject with my peers ...
I need some understanding as much as anyone else, but I do believe my
observations and questions are valid, and that I'll be able to
contribute as well as learn.
Comments in the context of your post follow ...
> On Thu, 18 Jan 2001 20:42:09 -0800 shAf
> ([EMAIL PROTECTED]) wrote:
>
> > Some values are so useless, they are even outside Lab
> > ... and not only can you not bringthem into gamut,
> > they should even be there in the first place ...
> > especially if we're talking about photography.
>
> Right, now I understand better what you are getting at and
> have no argument with most of it
> (apart from the philosophical one that RGB is
> device dependent so the purity and intensity of
> an eg pure blue depends on the device, not the RGB value -
I'll agree a device is capable of only some colors. With regard to
monitors, there is much of the working space's gamut we simply have to
accept on faith. We should be happy Photoshop's "monitor
compensation" at least removes the display's bias (influence) on the
perceived colors vs the RGB values.
There is of course usefulness in out-of-gamut colors ... for, as you
say, headroom, and because they can be brought into gamut. But surely
you'll agree some RGB values are so far out of gamut (relative to some
device gamuts and small working spaces), they can't be considered
useful (but surely archive the original image+gamut, you'll want them
later)
cheerios, shAf :o)
