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Creating Predictable, Accurate, Brand Colors for Inkjet Output

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Creating Predictable, Accurate, Brand Colors for Inkjet Output Creating Predictable, Accurate, Brand Colors for #COLOR19 Inkjet Output Peter Pretzer ColorPath Solutions Development Manager FUJIFILM North America Corp. Let’s start with some basics: § Human color perception § Illuminant § Object § Observer Color perception § Which square is darker? A or B? Color perception § Which square is darker? Color perception § Which circle is darker? Color perception § Which circle is darker? Color perception § Which circle is darker? Color perception § Which circle is darker? Color perception § Which circle is darker? Factors that affect color perception • Visual phenomena • Fatigue • Surrounding colors • Memory • Color deficiency § All humans see color • Viewing conditions/lighting differently… human analysis • Age is subjective, but necessary. • Sex Describe this color Warm red Apple red Pantone 185C 100 Magenta + 100 Yellow Red § Two things that are constant Cool red Fire engine red when talking about color: Beet red 1. Rarely does anyone agree on color 2. Everyone can tell you when the color is wrong Describe this color § Colorimetrically: § CIELab L* 57.40 a* 70.30 b* 43.10 § By appearance: § By recipe: § Candy-colored § 100 Magenta + 70 Yellow cherry-flake red § R: 231 G: 65 B: 66 § Pantone 185C What’s wrong with some recipes? Colorimetric: CIE L*a*b* space § Every specified color has an intersection point with L*, a*, and b* coordinates. § L: Brightness (0 to 100) § a: -Green +Red Axis (-127 to 127) § b: -Blue +Yellow Axis (-127 to 127) Spectral § Visible portion of the electromagnetic spectrum Spectral § Spectral Reflectance § Provides more information about color. § Other data can be derived from spectral data (L*a*b*, density) CxF/X-4 § ISO 17972-4: 2018 Graphic technology — Color data exchange format (CxF/X Part 4: Spot color characterization data § A more complete method of communicating color. CxF/X-4 § Initially developed by X-Rite § XML-like in structure/schema § Defines methods for exchanging measurement data and relate metadata in printable files (PDF). § Goal: minimize uncertainty of data exchanged and maximize flexibility. CxF/X-4 § Schema § Defines resources and attributes § Object § ColorValues § DeviceColorValues § Physical Attributes CxF/X-4 § Defines Resources § ObjectCollection § ColorValues (spectral, CIELab/XYZ/Luv, sRGB, Adobe RGB, density) § DeviceColorValues (RGB, CMYK, CMYK+N, HTML, HSL, recipes) § ColorDifferenceValues (∆E) § PhysicalAttributes (gloss, target, substrate type, size, weight, quantity) § TagCollections CxF/X-4 § Defines Resources § ColorSpecificationCollection § TristimulusSpec § Illuminant § Observer § Method § MeasurementSpec § PhysicalAttributes CxF/X-4 § Defines Resources § ColorSpecificationCollection § TristimulusSpec § MeasurementSpec § Type, geometry, wavelength range, luminance units, calibration standard, aperture size, background backing § Device § Manufacturer, model, serial number, class, device filter, device illumination, device polarization § PhysicalAttributes CxF/X-4 § Defines Resources § ColorSpecificationCollection § TristimulusSpec § MeasurementSpec § PhysicalAttributes § Target type, substrate type, finish type, quantity, height length, width, thickness, gloss, opacity, image, string, attributes (to describe methods, procedures, standards used, etc.) CxF/X-4 § Calculating Opacity CxF/X-4 § Three conformance levels: § Complete § Specifies color and opacity — for proofing of one spot color printed on top of another. § Single Background § A single ink printed on a single background. § Single Patch § A single ink always printed as a solid. CxF/X-4 § All things CxF: § https://www.xrite.com/categories/digital-color-standards/ color-exchange-format-cxf § Contains a whitepaper, a non-ISO copy of the standard, schema overviews and documentation. SCTV § ISO 20654 Graphic technology — Measurement and calculation of spot color tone value § Produces approximately uniform visual spacing of the tones between the unprinted substrate and the solid coverage. SCTV § The problem: § Historically, spot colors have been managed by measuring only the solid ink value, with no clear guidelines or methodology for calculating, simulating or measuring intermediate halftones. § Older methods (e.g. Murray Davies) do not work well for either measuring or predicting. SCTV § The problem: § What we expect… § What we get… SCTV § Color tints don’t print with equivalent gain § Printed with no SCTV § Printed using SCTV SCTV § The benefits: § Works predictably and repeatably with offset, digital, and flexo printing. § Easily implementable in front-end print production applications. § Ubiquitous in today’s measuring devices and color applications. § Aligns well with displayed results in creation software (Adobe, etc.) SCTV § Color tints don’t print with equivalent gain § Photoshop linear ramps § Printed using SCTV What about inkjet? What about inkjet? § Calibrate output device to a known, repeatable state § Limit inks, if not already done so in device controller § Linear and/or G7, if possible Ink Limiting § Prevents ink from rolling off substrate § Extends life of heads § Reduces effects of chroma hooks, resulting more predictable and accurate characterization Ink Limiting § Prevents ink from rolling off substrate § Reduces effects of chroma hooks (interpolation anomalies) § Extends life of heads Ink Limiting § Most higher end devices/ their controllers already do this § Pre-calculated and implemented by manufacturer § Take this into account when characterizing a device Device characterization TC1617 IT8.7/5 IT8.7/4 § CMYK § Use TC1617 or similar § Same number of patches as IT8.7/4 § Duplicate patches removed § Replaced with P2P rows 4 & 5 patches for G7/near neutral evaluation/alignment § Will be IT8.7/5 Device characterization § What about GCR/ink optimization? § Black generation algorithms already built in to existing devices/controllers § Attempting to add or change GCR will likely degrade the image § You should be using devicelink profiles for color management Device characterization § Other considerations: § Viewing conditions § ISO 3664:2009 is industry standard, but… Device characterization § Other considerations: § Viewing conditions § ISO 3664:2009 is industry standard, but… § Do the illuminant and substrate also affect color perception? Strategies for device alignment and separation § Working/Document Space § Source/Target § Destination Devicelink Profiles § What’s wrong with using § Iteration/optimization only ICC profiles ? yields tighter color matches for devicelink profiles § The optimization process can be highly automated (you don’t have to be an expert). Devicelink Profiles § Easily align a device and separate images to a source/target profile/CRPC Devicelink Profiles § Align a device and images § Iterative optimization to a source/target profile provides closer match to (e.g. CRPC 1-7) source § Align to a color exchange space § Control individual color channels (keep pure) § Control black generation CRPCs ISO DIS 15339 (Paper-Adapted)! § Easily align a device and images to a source/target profile § CRPC 1 – 7 (ISO 15339) § “Automatic” G7 1 2 3 4 5 6 7 56 Copyright © HutchColor, LLC CRPCs § Adjust white point of CRPC data set via SCCA (Substrate- Corrected Color Aims) Devicelink Profiles PRMG v2.0.1 vs CRPC6 § Align a device and images to a source/target profile (e.g. CRPC 1-7) or § Separate to a Large Gamut Exchange Space and gray balanced device profile § PRMG v2.0.1 vs CRPC6 Color Exchange Spaces § Not widely used § Not thoroughly tested § Some are proprietary § Profiles are available on the web, but licensing terms of use are undefined or unclear Named/brand colors Named Color Library/Lookup Table IT8 Chart ICC Profile Bracketing method § Print an array of colors, select the closest — or adjust-and-reprint until satisfied. § Currently available in most digital front ends. Bracketing method § Benefits: § Allows for subjective visual matching by brand managers, print buyers, color managers, and printing device operators. Bracketing method § Benefits: § Allows for subjective, visual evaluation and selection of in- and out-of-gamut colors. Bracketing method § Drawbacks: § Time-consuming! § Subjective § Less repeatable § Less accurate Iterative methods 1. Print all patches 2. Measure 3. Optimize 4. Repeat § Simple § Objective § Accurate § Fast! Iterative methods § Bracketing technology vs Colorimetric optimization § Bracketing technology + highly-skilled human: § 3.5 ∆E00 Out-of-gamut color § 1 – 2 Hrs. (per color) § Colorimetric optimization: § 3.4 ∆E00 Same out-of-gamut color § 20 minutes (entire Pantone® Library) Iterative methods § Can take advantage of automatically reducing patches in test charts § Generate only those patches that require further optimization. Iterative methods § Quickly re-calculate named color libraries due to variable print conditions § Use M1 or M2 measurement modes based on needs ECG device characterization § Channel-swap § Proprietary § Not portable (no ICC) Multicolor device characterization § CMYK + n § More portable (ICC) § Useful for 5 & 6 color § Multipurpose charts being developed § Grid points and TAC considered, e.g.: § 0-40-70-100 = 16,384 patches § 1,050 patches per chart page What about proofing? § Production inkjet presses provide flexibility § Wide format devices may require an existing proofing system to be aligned to duplicate possible in-gamut colors Color match: spectral / metameric? § Ink limiting considerations .
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