Re: Linear-light RAW 12bit vs R'G'B' 8bit: how much better is it really?
Re: Linear-light RAW 12bit vs R'G'B' 8bit: how much better is it really?
- Subject: Re: Linear-light RAW 12bit vs R'G'B' 8bit: how much better is it really?
- From: "email@hidden" <email@hidden>
- Date: Tue, 24 Jul 2007 08:36:03 -0500
When everyone was using imagesetters to make film for offset printing
they would "linearize" the imagesetter. This meant that when you said
that you wanted a 50% screen in illustrator the imagesetter would
output
a 50% dot on film. When you make a plate and print on paper you
get dot
gain. On the typical press you would get about 20% to 25% dot gain so
that the 50% dot on plate would print as a 70% to 75% dot on
paper. If
you plot the input dot area specified and measure the L* value out on
press, you will find that it is visually linear which means that
the end
to end gamma is about 2.2. Do to people linearizing their
imagesetters
they adopted the term with respect to inkjet proofers when they
usually
mean "calibrating" to a known condition rather than making them
linear.
The proofer has to emulate the dot gain on press and would not work if
it were "linear".
Hope this helps to understand the difference between energy linear vs.
visually linear.
Ray Maxwell
Not to argue, two questions really.
1) I had heard that the tonal response of ink on paper was closer to
1.8 gamma. I've tried to find out how to calculate this, but I can't
find anyone who knows. Do you know, Ray? If you can tell me how I'd
appreciate it.
2) Thinking about the quote about linear versus gamma corrected.
Suppose a person walked with the same size steps all the time. If he
walks on a straight road, he takes 256 steps to cover a certain
distance. If the same straight-line distance were covered by a road
that curved - amazingly to exactly display a 2.2 gamma (or non-
linearity) - would it then take this person 2048 steps to go from end
to end? Is this what he means?
Rich Apollo
G7 Certified Expert
Adobe Certified Expert, Photoshop
314-344-1144
email@hidden
www.prioritylitho.com
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