Color Impact 2023 was a great success. These pages are left here for archival purposes.

We hope to see you at a future Color Council meeting! Our next conference in June 2025.

June 11-15, 2023

Rochester Institute of Technology, Rochester, NY, USA

Presenter - Carinna Parraman

Carinna Parraman, Educator and Researcher

RGB Colour Printing and Halftoning for the Reproduction of Structural Colour Images

Commercial CMYK halftone printing involves additive and subtractive colour mixing that requires the optical mixing of primary colour hues using different-sized dots to obtain variations in reflected colour.

Structural colour, as seen in nature, such as in birds, butterflies and shells, is based on the scattering of light that uses micron to submicron structures to reflect specific wavelengths of light.

Similar to CMYK printing, so-called RGB special effect pigment colours mimic the appearance of these structures by combining additive and subtractive methods to create a range of colours. Similar to structural colour, these pigments, when printed, are highly dynamic in their angle of appearance and surface scattering. This dynamic appearance also presents new problems both in terms of reproduction, appearance and measurement.

We have studied the influence of different halftone structures on an RGB print using various printing methods. First-order, second-order, and structure-aware FM halftoning algorithms were applied to produce different spatial combinations of inks on the printed surface.

The images must be printed on a black substrate, and the pigments present quite an unusual gamut. The image content of the print needs to be chosen carefully, which, erring towards the blue-green area of the spectrum, has a strong correlation with images that exploit the original features ie feathers and beetle shells.

We aim to optimise the printing method and halftone pattern to reproduce particular images. This paper will present how different structure-aware halftones improve the representation of image structures and details.

Halftone structures differ in the spatial distribution of dots. For instance, in first-order FM halftones, single dots are distributed stochastically, where the size of dots is constant while their density is changed. In second-order FM (also known as stochastic cluster-dot halftone), the size and the distance between dots are variable. To improve the reproduction of structural detail, the structure-aware algorithm seeks to place dots in line with the high-frequency areas of the image.


Dr. Carinna Parraman is Professor of Design, Colour and Print and Director of the Centre for Print Research, at the University of the West of England, Bristol. As Director of CFPR, she leads a cross-disciplinary research team comprising expertise including scientists and technologists, designers and artists. The CFPR group are exploring the future of printing and fabrication, new ways of thinking and working alongside traditional methods of making. Her work spans art and science, including colour mixing, colour printing, texture appearance and photomechanical printing processes. She collaborates with different sectors, including industry, heritage and fine art print. Her print practice explores colour mixing of patterns, elements and halftones that dazzle and vibrate. She is experimenting with using RGB pigments on black paper to create new colour appearances. She is also a collector of paint colour charts and real-world colours #colouraday. 

The Inter-Society Color Council advances the knowledge of color as it relates to art, science, industry and design.
Each of these fields enriches the others, furthering the general objective of color education.


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