The colour difference formula CIEDE2000 and its performance with a graphic arts data set

Abstract

The magnitude of colour difference which may be accepted for critical comparisons in graphic arts colour reproduction was investigated using 10 colour centres printed by offset lithography. Visual assessments were made by a panel of observers, and the data has been used to determine acceptability thresholds and optimise the parametric factors in the colour difference equations CIE94 and CIEDE2000. The performance of these equations, with and without these parametric factors, has been compared to 1976 CIELAB colour difference. The results showed a small improvement in performance for both equations, although neither model successfully predicted the visual difference of the black samples. Acceptability tolerances of 4 in CIELAB and 3 for CIE94 and CIEDE2000 are proposed, and optimised parametric factors were calculated for weighting lightness, chroma and hue of 1.5:1:0.5 respectively.

Tony Johnson

Research Interests
• Colour Imaging
• Gloss
• Colour measurement
• Image Processing
• Printing Technology

Current Research

Since the end of 2004 I have largely retired but prior to that I spent over 30 years working in colour imaging research for the printing industry. I helped develop many colour and image processing algorithms for electronic imaging and undertook research in many aspects of colour reproduction by printing. I was also heavily involved in international standardisation for printing for many years.

During my last 10 years prior to retirement, as well as being a Professor at the LCP undertaking both research and teaching in colour imaging, I undertook consultancy work in colour imaging. Prior to that I worked in research for both Pira and Crosfield Electronics who, at that time, was one of the market leaders in electronic colour imaging.

I am in the process of publishing papers based on my research activity prior to retirement, dealing with the measurement of gloss and its effect on colour management. My time at LCC is now spent supervising research students. Currently I am supervising 5 postgraduate students working on various aspects of colour imaging, including colour management on non-paper substrates, colour difference measurement for complex images, colour image quality measurement, n-colour printing.