Understanding ICC, RGB, CMYK, HSB, and Lab in Inkjet Printing
ICC, RGB, CMYK, HSB, and Lab in Inkjet Printing
The Concept of ICC Profiles
ICC is the abbreviation of the International Color Consortium. The ICC established a unified color management system to ensure color consistency across different operating systems, devices, and software.
In color printing, color shifts often occur—meaning the printed output does not match what is displayed on the computer screen. This is mainly caused by the difference between the RGB color gamut used by monitors and the CMYK color gamut used by printers.
RGB Color Space
The RGB color space is based on the three primary colors of light: Red, Green, and Blue. It is an additive color model widely used in display devices such as televisions, computer monitors, and smartphone screens.
In RGB mode, colors are created by adjusting the intensity of the R, G, and B channels. RGB can represent nearly all colors visible to the human eye and supports 16,777,216 colors per pixel (256 × 256 × 256), making it one of the most widely used color systems.
The RGB color gamut is relatively limited compared with some extended color spaces. Common RGB standards include sRGB and Adobe RGB, with sRGB being the most widely used. The “s” stands for standard. sRGB was jointly developed by Microsoft, HP, Mitsubishi, Epson, and others as a universal color standard.
Different devices support RGB gamuts differently. High-end displays may support wider color gamuts such as Adobe RGB or DCI-P3, delivering richer color performance. Therefore, understanding a display’s color gamut capability is crucial when selecting professional equipment.
CMYK Color Space
The CMYK color space represents the color range produced by mixing Cyan (C), Magenta (M), Yellow (Y), and Black (K) inks. It is primarily used in the printing industry.
Unlike RGB, which is based on light, CMYK is a subtractive color model based on ink absorption. CMYK has a smaller color gamut than RGB, meaning it cannot reproduce all colors visible on screens. As a result, color depth and brightness variations are more limited.
Converting images to CMYK before printing ensures better color accuracy in printed output. However, when CMYK images are displayed on RGB devices, some colors may appear distorted or muted due to gamut differences.
In summary, CMYK is a print-oriented color space optimized for ink-based reproduction and differs significantly from RGB in both application and color range.
Lab Color Space (CIELAB)
Lab, formally known as CIELAB, is a color model defined by the Commission Internationale de l'Éclairage (CIE). It was established in 1931 and refined in 1976.
Lab compensates for the limitations of RGB and CMYK. It is a device-independent and human-vision-based color model.
The Lab color model consists of three components:
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L: Lightness (0–100, from black to white)
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a: Green (–128) to red (+127)
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b: Blue (–128) to yellow (+127)
Lab covers a color gamut larger than both display devices and human vision. Bitmaps in Lab require more data than RGB or CMYK to achieve the same precision. However, Lab provides the most comprehensive color definition, is independent of devices and lighting, and processes as fast as RGB.
HSB Color Space
HSB (Hue, Saturation, Brightness) is a color model designed to align closely with human visual perception.
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Hue (H): The basic color type, represented as an angle from 0° to 360°
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Saturation (S): Color purity, ranging from 0% (gray) to 100% (pure color)
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Brightness (B): Lightness of the color, ranging from 0% (black) to 100% (white)
HSB is widely used in design software due to its intuitive nature. Designers can easily adjust hue, saturation, and brightness to achieve desired visual effects.
Causes of Color Deviation in Printing
Reason ①: Color Space Translation
Computers and displays generate colors in RGB, while printers use CMYK (or extended modes such as CMYK + LC + LM). When color data is transferred from software (e.g., Photoshop) to the printer, it must be translated. Differences in interpretation can cause color deviation.
Reason ②: Material and Ink Interaction
Different substrates—such as vinyl, PP paper, transparent plastics, and PVC—react differently with inks due to coating chemistry. Ink absorption and dot gain vary, requiring correction. ICC profiles compensate for these differences.
Reason ③: Device and Software Variability
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Different printhead generations (e.g., Epson first-generation vs. fourth-generation) interpret and execute commands differently.
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Even with identical ink, substrate, software, and control boards, different printers require individual ICC profiles.
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Using different printheads or RIP software can also cause output variations.
How ICC Profiles Are Created
ICC profiles are typically created using color management systems such as X-Rite tools.
The process involves:
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Printing standardized color patches on the target substrate
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Measuring the printed patches with a spectrophotometer
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Comparing measured values with reference values
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Generating an ICC profile based on the color deviation data
Summary
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Different substrates require different ICC profiles.
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Different inks require different ICC profiles.
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Desktop printers often have built-in color correction and do not require custom ICC profiles.
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Large-format printers using third-party RIP software must load custom ICC profiles for each specific material.
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Using incorrect ICC profiles results in suboptimal print quality.
ICC profiles are critical for achieving accurate and consistent color output in inkjet printing.
Knowledge Extension
Among RGB, CMYK, HSB, and Lab, Lab has the largest color gamut.
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Lab covers all colors perceivable by the human eye and is device-independent.
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HSB follows Lab in gamut size.
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RGB is next.
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CMYK has the smallest gamut.
Conclusion:
Lab is the most comprehensive color space and the best reference model among the four, especially for color management and conversion.
