Standards-based inkjet proofing ABC_1
Standards-based inkjet proofing ABC_1
- Subject: Standards-based inkjet proofing ABC_1
- From: Henrik Holmegaard <email@hidden>
- Date: Sat, 3 Nov 2001 09:54:16 +0100
You are most likely already using standards-based ICC output
profiles. This post describes why you should use standards-based
proofing, and how to go about it. The post comes in separate parts.
What is an RGB workflow:
In a device independent workflow, conversions are fully modular. The
Source space needs to know nothing about the Output space, and the
Output space nothing about the Destination space. RGB Source1 may be
converted into CMYK Output1, CMYK Output2, CMYK Output...n just as
well as simulated (: proof printed) into CMYK Destination1, CMYK
Destination2, CMYK Destination...n and typically also simulated (:
soft-proofed) into RGB Destination1, RGB Destination2, RGB
Destination...n.
As long as the color spaces in the chain are described by industry
standard ICC device profiles, you are free to create an RGB digital
original that separates well to standards-based output, and repurpose
that original at any site and in any schedule you want. Instead of
saying that an ICC device profile workflow modularizes color space
conversions, you can say that it offers late binding (because the
binding loss of saturation and lightness is late) or scan once output
many or simply that it is 'an RGB workflow'.
In an RGB workflow you do not have to know what specific output
process the data will be reproduced by. But if you do not know the
output process for RGB and Lab digital originals, how do you tell
that you have a proof, and hence a sellable CMYK product? A studio
inkjet print is in itself no guarantee since an inkjet supports many
colors an offset process doesn't. So there has to a simple method of
telling if the gamut of the studio printer has been cropped to the
gamut of a printing process.
International printing standards:
Manufacturers of PostScript-enabled publishing software including
Adobe bundle output profiles built from two sets of standards, the
global ISO 12647-2 (offset for four paper types and positive and
negative plate, making eight data sets), ISO 12647-3 (newsprint) and
the US-only TR001 printing standard. For instance, standards-based
output profiles are found on www.profilecentral.com, in your System
ICC profiles folder where they are installed by Adobe applications,
and in BESTColor systems.
The ISO standard relies on averaged LAB characterization data of the
test chart formerly known as IT8.7-3 which you will find on the Mac
OS CD in the ColorSync folder. The measurements are averaged from
real press runs, and the ISO data can be downloaded free of charge
from,
a. www.fogra.org, honorary member of and midwife to the ICC,
b. www.color.org which is the home page of the ICC,
for use in ProfileMaker Professional and any other tool that offers
advanced separation settings and supports this particular test chart
layout. Back in '97 FOGRA posted ICC profiles on its site, in
addition to the eight characterization data sets. This policy has ceasede
because no two profiling applications are alike in their black generation and
gamut mapping functionality.
FOGRA's Fred Dolezalek is chair of ISO TC 130 Graphic Technology,
which is the relevant standard, and FOGRA also supplies proofing
validation materials.
You need the following software and hardware items:
c. the UGRA/FOGRA Media Wedge CMYK proof validation strip which comes
as TIFF and EPS / PDF with 34 chromatic and nine non-chromatic K only
patches from the first printing point up to 100 % solid, plus the
FOGRA proof validation spreadsheet which verifies both ISO 12647-2,
ISO 12647-3 and on a transatlantic note also TR001 proofs.
d. a spot-reading spectrophotometer (those with a Spectrolino may use
the KeyWizard utility for data transfer, the rest of us are stuck
with typing the values from Eye-One Share, ColorPicker or MeaureTool
readings into the FOGRA spreadsheet),
e. a stable and calibratable high gamut inkjet (as you can easily
verify with LOGO ColorLab or the ProfileMaker MeasureTool, color
copiers and color laser printer are as a rule not stable enough for
proofing, and dye sublimation and thermal wax printers are for many
reasons now technically marginalized),
f. a standards-based ICC output profile created from the LAB
characterization data available from www.fogra.org,
g. optionally, an ICC color server which will color manage a control
strip outside your netto page area, for instance, iQueue from
GretagMacbeth or BESTColor from BEST.
(End part 1)