Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
...
> I understood you.  I guess I was raising the counter question that
if there
> is little difference in grey scale between 2.2 gamma and LAB (see
Bruce's
> curves) then what is gained by output at LAB?

Well, it's a choice that was made. You'd have to ask Roy. But it seems
a likely choice given that all out icc based color output it
referenced to it too. You have to pick something right? It seems no
one picks the same target to hit.

...
then a bunch of math stuff...
Steve, not going there. NOT GONNA DO IT!
The excedrin bottle is nearly empty, the dog needs to go out, my
clients are screaming, my butt hurts...

How about this? If the output dynamic range is by nature smaller than
the "abstract" space of say, LAB, then there is indeed compression, right?
And what you are saying is that even if one "linearizes to LAB" that
output to the smaller range that the resulting slope is no longer the
same as LAB, right?
These working spaces are simply that, descriptors. There is no real
world equivalent of absolute black or white that is relevant to us
with this work. When translated to any useful viewing of the art,
whether monitor, paper, whatever, there is by nature always a
compression if the image content utilizes the full range of the
working space.
The resulting tonal progression is something porportionally or somehow
mathematically related to the reference, but not exactly the same rate
of change. If we insist on maintaining that slope in some part of the
scale, then yes, there would be something clipped, or compressed at
the extremes, or whatever.
But what would be the point? What is so sancrosanct about maintaining
that slope somewhere? The whole point is to maintain the tonal
relationships, unless of course you want come up with your own unique
definition of "linearization".

Also, this all flies in the face of maintaining some standard middle
gray density value. If I linearize uncoated Somerset Velvet (low dmax)
and PhotoRag (high dmax) middle gray value in the file will print
differently on one paper than the other. Rightly so! I want those
relationships I worked so hard on maintained. If I want to match some
gray on both prints, obviously I'll have to massively compress my
shadow values in the uncoated version. The concept of middle gray has
been redefined. Now it really IS in the middle. Actually it always was
for us zone freaks, gray card be damned.
If that's what one is attempting (a specific middle gray target
density), every paper and ink combination would have to be linearized
to a different gamma, based on paper white and dmax, and the tonal
relationships in a file when printed on them all would be different.

Is this getting to what you are talking about? If so, I can only say
that to my knowledge, linearization by today's standard means a
uniform compression as above, so then a deviation from the strict
slope of the reference space. I think that's what you have been trying
to get me to absorb.
But I'm not sure there is another really useful way to go about this.
If you come up with one, be careful who you share it with before you
make your own trip to the patent office <G>.
If you are attempting to point out that the process of linearization
to a given standard like LAB is not strictly the same as the reference
and therefore not really "linearization" then yes, you are right.
I think I get your point now, if not, please forgive me, I have to
take the dog out.
Tyler

By the way, by strict definition, colormetric icc color
transformations maintain the relationships as you suggest from paper
white on down with Black Point Compensation off, then of course the
shadows clip if out of gamut. Someone correct me if that's wrong.