Hi Shaf, Tony.
shAf wrote:
> Tony writes ...
>
> > On Fri, 19 Jan 2001 22:28:59 +0000 Photoscientia
> > ([EMAIL PROTECTED]) wrote:
> >
> > > CIE L*a*b* is poorly suited to DTP applications in three main
> areas:
> >
> > The main objection to CIELAB for DTP is (AFAIK) that DTP
> > is (professionally) always done in CMYK for pre-press output -
> > eg Pantone is CMYK gamut - and CIELAB is an RGB space.
>
> I would object to L*a*b, as any application space, simply because
> it
> is unintuitive. My own questions regarding it are only in the context
> of
> it being a absolute reference ... otherwise (practically) useless.
Hear hear, Shaf.
BTW those words about CIELAB and DTP weren't mine. They were extracted
from a well argued paper on the subject by a very knowledgable colour
scientist.
I would add, though, that no matter how accurate a reference or not
CIELAB
is, what it certainly isn't is portable, or practically useful to the
average user.
How many people can lay their hands on a CIE reference light source?
Then, having got your light source, now what? There's no way to
reconstruct a colour from it's L*a*b* specification, apart from trial
and
error, mixing standard pigments with a CIE calibrated colorimeter, and
of
course, we all have one of those handy in our back pocket.
You don't? Pity. But I suspect you have a perfectly useable colour
reconstruction device sitting right in front of you now. An RGB monitor.
Forget L*a*b*, you need an entire lab(oratory) to make proper use of it,
unless, of course, you convert it to RGB first.
Now in defense of RGB:
The phosphors in monitors aren't all different. They're usually one of a
standard set.
The first thing I do with a new monitor is to set up the colour balance
in
hardware (this involves taking the back off, in most cases). I match the
white point to north daylight by eye with the gun gains, and adjust the
RGB black levels for a neutral greyscale, and just invisible raster. The
settings interact, and it's time consuming. Even after a lot of practise
it still takes up to half an hour, but what it doesn't take is a roomful
of special equipment.
I've found that a monitor set up like this by eye alone will match
almost
any other monitor set up the same way, within very close limits. These
monitors aren't used for any special graphics purpose, just workstation
clusters, but it's nicer to see a row of monitors that all look the
same.
So what's the point of that anecdote? Well, if the manufacturers could
be
bothered to do the same thing, using a standard electronic substitute
for
my Mk1, then I don't think there'd be half the moaning there is about
RGB
spaces. In fact, I'm sure it's not beyond the wit of man to make all
monitors self-calibrating in some way, thus compensating for ageing,
drift
and user abuse.
Then we could completely throw CIELAB out of the window, or Macos, as
the
case may be.
As things stand, all we've got is half the equation, with the sRGB
specification laying down standards that people just ignore.
Regards, Pete.
