Post on 23-Mar-2021
#COLOR19Oiling Your Color
Management MachineJohn Seymour
John the Math Guy, LLC
John the Math Guy
Color management in a nutshell
§Accurate communication of color between print buyer and printer
§Accurate production of color by printer
ICC Profile – the main tool
Converts fromone description
of color…
… into another
ICC Profile – the Rosetta StoneHieroglyphic
Demotic
Ancient Greek
ICC Profile – the main tool
Generally,one description
is device dependent...
… and the other is device
independent.
Dependent? Independent?
§Device dependent§CMYK§RGB§CMYKOGV
§Ambiguous
§Device independent§ L*a*b*§ sRGB§XYZ
§Standardized
ICC Profile to communicate intent
So that a given CMYK value…
… is interpreted as a given
L*a*b* value.
CGATS TR002, Fogra 54, ISO 15339 CRPC 2 … User specifies a profile
Communication profiles
§Based on hypothetical press§Running hypothetical inks§On hypothetical stock§With a hypothetical pressman
Testing artwork with a prooferJMG Times
CMYKvalues
L*a*b*values
CRPC 4, communication profile
Prediction profile
CMYKvalues
JMG Times
InstaProof
Producing artwork on pressJMG Times
CMYKvalues
L*a*b*values
CRPC 4, communication profile
Prediction profile
CMYKvalues
Prediction profile
Prediction profile?
Prediction profile
The IT8 test target
Prediction profile
§Press is set to standard condition when profiled§Press is reset to that same standard condition for
production
How do you reach this standard condition?
Oilhere
Oilhere
Oilhere
OilhereOil
hereOilhere
Oilhere
Oilhere
Oilhere
Color management isn’t all that complicated
Color management isn’t all that complicated• You just have to know where to apply the oil• And how much to apply• And what type of oil for each point
• Ok… maybe it is a bit complicated!
My view of what color management means• Applies to all places that affect color• Not just profiling the press• Today we talk about all those other places
Oiling the SOLID CMYK gear
Solid CYMK
• Targets defined in ISO 12647-2 and ISO 12647-6• May be defined in a CxF file• Substrate correction may be allowed/required• ISO 12647-2 (web offset) – target is L*a*b*, not density• ISO 12647-6 (flexo) – target is a CIELAB hue angle
What!??!?!?!
Perifarbe concept• Adjust ink strength or
film thickness• Run to the density
closest to target L*a*b*
Perifarbe in practice
Oiling Single-ink CMYK halftones
Oiling Single-ink CMYK halftones
Actual press Target
Tone valuein file
Tone valuefor plate
Oiling Single-ink CMYK halftones
• Set up plate curves to adjust
• Use the TVI formula (“Murray-Davies”) to match TVI curves in ISO 12647
Oiling Single-ink CMYK halftones (G7 method)
Single ink halftones of CMYK (G7 method)• Motivation
• Grays are more important than single color halftones• Common appearance is possible
• Specific CMY combinations (e.g. C50, M40, Y40) are ordered to be a specific gray
• Plates curves adjusted to make neutral
G7 in a single imageY40 41 423938
38
39
41
40
42
M
C50Want this to be gray
Single ink halftones of CMYK (G7 method)• Motivation
• Grays are more important than single color halftones• Common appearance is possible
• Specific CMY combinations (e.g. C50, M40, Y40) are ordered to be gray
• Plates curves adjusted to make neutral• Not fully compatible with TVI method – do one or the other• The results are similar, usually• ISO characterization data sets are based on G7
So far…
• Solids are adjusted at press• or maybe in the ink room?
• Halftones adjusted via plate curve to match either TVI or G7 spec
• Solids and plate curves plus communication profile might be good enough
Overprints?
Overprints
• Overprints are tough
Where was that overprint knob???
???
Overprints
• Overprints are tough• Depend on the solids• Depend on tack and opacity• L*a*b* target values are in 12647-2• But there are no DE tolerances
(Preucil) trap number• Could be a useful check• Could be misleading • Not recommended by ISO
Overprints
• Overprints are tough• Depend on solids• Depend on tack and opacity• L*a*b* target values are in 12647-2• But there are no DE tolerances• Where to put the oil?
So far…
• Solids are adjusted at press• Halftones adjusted via plate curve to match either TVI
or G7 spec• Overprints adjusted at press or ink room or ink
company or no where?
The rest of the CMYK builds
The rest of the CMYK builds
• Getting proper CMYK solids and TVI or G7 might be close enough?
• Assumes that your press “behaves like the hypothetical press”
• Example where they don’t – stochastic vs conventional dots
• Example where they don’t – two and three color overprints
• If not good enough, full on color management with profiles is necessary
Spot colors
• Target is • A cloth swatch• PMS number• L*a*b* value• Spectrum
• CxF
Spot color formulation
• Performed in ink kitchen• Can be adjusted by hand• More better to do with formulation software
Spot color formulation
Spot color on press• Big question
• Can we get there from here?
• … or do we need to go back to the kitchen?
Halftones of Spot colors• Usually not specified!• Use TVI for plate curves?
• What filter?• What TVI curve?
• Warning – TVI fails for rich colors and tints
• Use SCTV (Spot Color Tone Value)
So far…
• Solids are adjusted at press• Halftones adjusted via plate curve to match either TVI
or G7 spec• Overprints adjusted at press or ink room or ink
company?• Ink formulation software for spot colors• SCTV for plate curves of spot color halftones
Expanded gamut
• Will allow richer colors (orange, green, and blue) in images
CMYK gamut CMYK+OGV gamut
Expanded gamut
• Will allow richer colors (orange, green, and blue) in images
• (Big sell point) ~90% of spot colors can be printed with CMYKOGV
• Less cleanup between runs – huge savings for short run plants
Expanded gamut – downsides
• Expect to invest• Requires press profiling• Special software• Learning curve
• No universal standard set of inks• Red or orange?• Blue or violet?• Maybe CMYKOG?
• No industry standard 7-color profiles
EG color management of solids
• You decide O vs R, and V vs B• You decide target L*a*b* of O, G, and V
This gamut ain’t big enough for the both of us!!
Are we in the wild west?
EG color management of solids
• You decide O vs R, and V vs B• You decide target L*a*b* of O, G, and V• Same perifarbe stuff applies
EG color management of halftones
• TVI or SCTV?• Best guess today
• use SCTV for OGV• use TVI for CMYK
• In the future?• Perhaps SCTV for CMYK as well
Review• Solids are adjusted at press• Halftones adjusted via plate curve to match either TVI or
G7 spec• Overprints adjusted at press or ink room or ink company?• Ink formulation software for spot colors• SCTV for plate curves of spot color halftones• Expanded gamut
• use perifarbe to reach your target• use SCTV to set plate curves
This presentationis largely based on a webinar
I presented forTechkon USA, Feb 2018.
I gratefully acknowledge being permitted to reuse this
material.
#COLOR19 John SeymourJohn the Math Guy, LLC
john@johnthemathguy.comhttp://johnthemathguy.blogspot.com/
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John the Math Guy