Printing Standards & Specifications Flashcards
What’s does GRACol stand for ?
General requirements and applications for commercial offset lithography
What does SWOP stand for?
Specifications for web offset publications
What does SNAP stand for?
Specifications for newsprint advertising production
What is ISO 12647
- The official international printing standard
- Defines ink/paper colour, dot gain etc.
- Universal basis for print specs (SWOP, GRACol, ICC etc.)
WhT Re Colorimetic Specifications?
Defined by characterization data sets
Must be tested yearly
What is densitomerty?
- Measures ink quantity but not ink colour
- Convenient for CMYK process control
- Less useful for colour matching
- Doesn’t measure appearance
What is Colorimetry?
- Measures ink colour precisely
- Less convenient process control
- Excellent for colour matching
- Measures visual appearance
Colorimetry basics involve this formula
CIELab = numerical definition of human vision
For the CIELab:
Lowest L value = 0 (black)
Highest L value = 100 (white)
What is the unit of CIELab colour
Delta E
What does 0 delta E mean?
It means there is NO different in colour (only in a perfect world)
What delta E value = limit of visual perception
Less than 1.0
What delta E value = typical proof tolerance
Less than 2.0
What delta e = good press tolerance
Less than 5.0
Delta E is the..
Difference btwn colour on swatch to match colour on press sheet
SWOP is intended for
Web offset publications on coated paper
GRACol was developed for
Commercial sheetfed offset lithography
SNAP is intended for
Newspaper industry (including ads printed in newspaper) Coldset newspaper printing
What is G7
New method for calibrating a press or proofer
Bases of both current SWOP11 and GRACol 7
Based on visual metrics
Brings photographic principles to press
Controls Gray balance and neutral tonality (which TVI doesn’t)
G7 is named for…
G = gray scale
7 = seven ISO ink solids
Trade mark of IDEAlliance
Limitations ofmTVI calibration
- Identical CMY TVI curves can produce different neutral contrast and/or gray balance
- Doesn’t control gray tonality b/c ignore 3-colour ink trap
- CMY TVI curves don’t control gray balance b/c they ignore ink trap, opacity,hue
How many scales does G7 calibration measure?
2 scales
- K-only
- Gray balance
By using look up tables (LUTs) G7 calibration controls….
Neutral contrast & gray balance
Benefits of G7 are…
- Directly Controls neutral tonality & gray balance using same RIP curves as TVI
- CMY gray scales measures visual affects 3-colour trap for precise gray tonality
- CMY gray scale measures and controls the combined effects of ink trap, ink opacity and hue for precise gray balance
G7 ink =
ISO ink
G7 paper =
ISO paper
All G7- based printing methods share
- Same gray balance & tonal contrast
2. Less need to convert files separated for another process
A specification is based on
A standard
IDEAAlluance does not make
Standards
IDEAlliance’s mission is to
Promote & implement standards like ISO 12647-2
And develop moods where needed
