Re: Total Ink Limit (TAC)
Re: Total Ink Limit (TAC)
- Subject: Re: Total Ink Limit (TAC)
- From: Terence Wyse <email@hidden>
- Date: Sat, 10 May 2008 12:23:07 -0400
On May 10, 2008, at 5:28 AM, Dan Wilson wrote:
Hi & thanks for all the expert discussions on this forum.
In an ICC transformation does the Total Ink Limit (TAC) get changed?
Yes, but maybe not in the way you expect based on the color transform
you describe below.
Example:
On a proofer with a RIP, if I have a file that is being used for
sheetfed
with say 340 ink limit and I want to proof it for newspaper at say
220, does
the ICC transform change the ink limit to 220 so that my proof will be
accurate for newsprint?
Depends but I would say "no", not in the way you expect.
If you have a file separated for 340% TAC and you send it UNTAGGED to
a proofing system with "Newspaper" as source and "inkjet" as
destination, what you'll get is an attempt to simulate 340% TAC on
"Newspaper". The only TAC limit in this conversion would be the TAC
that the "inkjet" profile imposes on the output. In essence, the image
with 340% TAC gets ASSIGNED the "Newspaper" profile and then proofed
through the "inkjet" profile.
What you MIGHT be looking for is what happens when a *simulation*
profile is introduce into the CM transform. In this scenario, you set
your original profile (the one with the 340% TAC) as source with
"Newspaper" as simulation and, finally, "inkjet" as output/
destination. The transform goes like this:
"340% TAC" (source) profile --> "Newspaper" (simulation) profile -->
"inkjet" (destination) profile.
So in this case, the 340% TAC image gets converted to "Newspaper"
where a 220% TAC is imposed and then finally to the "inkjet" profile
where the inkjet TAC is imposed. The intention of the simulation
profile is to simulate this intermediate conversion before sending it
for the final proofing output.
But most proofing systems are NOT set up this way since this proof is
"false" meaning that its performing a conversion to the image for
proofing only but does really reflect a proof from the original image.
I assume it would map the colours from the original colour space to
the
target colour space (relative colorimetric) reducing the TAC in the
process.
No, the newspaper profile is simply getting *assigned* to the image.
The proof would basically reflect how the original CMYK values would
print (including the excess TAC) on newspaper.
I understand the file has not changed and will need to be adjusted
later
(maybe with a device link) to be suitable for the newspaper press.
Am I understanding this correctly?
Thanks,
Dan Wilson
Regards,
Terry Wyse
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