Re: Total Ink Limit (TAC)
Re: Total Ink Limit (TAC)
- Subject: Re: Total Ink Limit (TAC)
- From: email@hidden
- Date: Tue, 13 May 2008 10:19:31 +1000
Dear Dan,
At first I thought this was a surprising question coming from you however, it does highlight a lot of
problems. To me most of them are simply bad practice. Unless you have found a RIP or conversion tool
to 'reverse engineer' the 340% profile into a 220% newsprint profile I think this you are esentially
trying to turn a silk purse into a dog's breakfast. Let's face it - a newsprint job is never going to look
like a glossy magazine.
In Graeme's typically circumspect way he has highlight the core problem...
> There is much greater confidence in processing the image using
> the press workflow, and then proofing that.
>
> Graeme Gill.
>
Graeme, correct if I'm wrong but I think you are saying that the best way to go would be to make a
newsprint version from the original, source, RGB files. If you don't have those at hand you're trying to
do something ICC never intended (to my mind at least).
Proofing RIPs are designed to remap CMYK press profiles into the WIDER gamut of the proofing device
(inkjet printer?). I know I might be stating the obvious but, as these printing devices were never
originally designed with proofing as their main purpose in life this is difficult and that is why we buy
expnsive software to do it properly. In other words, sending a CMYK file destined for one device (a
press) and print it accurately on another (inkjet printer). Having said that I don't think they were
intended to remap a larger colour space into a smaller one which is essntially what you are trying to
do. I know you CAN do it but you have to ask is this what it was designed for?
Of course, you don't HAVE to have a RIP to make a proof. You can print from any Adobe application
using Absolute Colorimateric rendering Intent to convert from one CMYK profile to another but how do
you do this if the source is larger than the destination?
Adding to this there are other problems. Normally, I would say that contemplating a conversion from a
340% TAC file to a 220% profile only exposes a limited understanding of the behaviour of printing inks,
substrates and printing processes. A (properly constructed) newspaper profile will have a completely
different GCR/UCR and Black generation specification based on the low viscosity inks and highly
absorbent uncoated stock not to mention the relatively high speed of the press. How do you reverse
engineer this? To my mimd the short answer is... you don't. OR you shouldn't. Without GCR or any
black generation it is possible to recreate the RGB values for the separation setup (a la the Hutcheson
Crosfield drum scanner profiling method) from which you could then create a proper newsprint profile
with appropriate GCR and Black generation.
In summary, you can use a DeviceLink profile to convert the newsprint profile into something that the
proofing device can accurately render but having exactly the same separation setup is not the goal
here. Producing something that is COLORIMETRICALLY and visually accurate for the purposes of
proofing is. Getting the 340% profile into the newsprint colour space with the right separation setup is
the problem.
Mark Stegman
Teacher
Graphic Prepress
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