Development of softcopy environment for color banding assessment

Byungseok Min, Purdue University

Abstract

Fine-pitch banding is perceived as a quasiperiodic fluctuation in the process direction. The color banding signal arises from the independent contributions of the four primary colorant banding signals, but, it is not known how these four distinct signals combine to give rise to the perception of color banding. In this paper, we introduce a methodology to assess the color banding visibility based on human visual perception. In the primary banding, we extract the banding profile from a scanned primary colorant image as a one dimensional signal so that we can associate it with the one dimensional perception freely adjust the intensity of banding. Thereafter, by exploiting the pulse width modulation (PWM) capability of the laser printer, the extracted banding profile is used to modulate the extrinsic banding in the hardcopy environment. Furthermore, to conduct various banding assessments more efficiently, we also develop a softcopy environment that emulates a hardcopy image on a calibrated monitor. To achieve the same color appearance as the hardcopy, we perform haploscopic matching experiments that allow each eye to independently adapt to different viewing conditions; and we find an appearance mapping function in the adapted XYZ space. Thereafter, the softcopy environment was validated by the banding level matching experiment as well as by two separate differential threshold experiments in the hardcopy and softcopy environment. In the secondary colorant banding, we characterize the intrinsic banding by ΔL,ΔH, and Δ LCH banding respectively from luminance, hue, and whole L*[special characters omitted]Hab variation from the average L*[special characters omitted]Hab value of the test stimuli. After validating the softcopy environment by the banding level experiment for C (cyan), M (magenta) and CM (cyan+magenta), we measured and compared the absolute thresholds of ΔLCH banding of the C,M and CM by means of the signal detection method, to investigate how two primary banding and the secondary banding are related. Thereafter, we performed additional experiments to measured AL of ΔL banding and Hue banding to see their impact to ΔLCH banding. As a result, we found that luminance variation dominates the perception of whole ΔLCH banding, but chroma and hue variation do not have the influence on the banding.

Degree

Ph.D.

Advisors

Pizlo, Purdue University.

Subject Area

Electrical engineering

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