Measuring Visual Threshold of Inkjet Banding

Banding can be a major defect in inkjet printing. Knowing the visual sensitivity threshold of inkjet banding is therefore useful for understanding and pushing the technological limit of inkjet printing. There are many reports on the measurement of the human contrast sensitivity using self-luminous sinusoidal contrast targets. There are also reports on measuring the contrast sensitivity of sinusoidal banding on hardcopy targets. However, there has been no report on measuring visual threshold of banding defects that are characteristic of inkjet printing, which is usually not sinusoidal, despite the evidence that the visual threshold of a complex pattern may not be able to be predicted based on each of its harmonic components. In this paper, we report a study on measuring the human visual threshold of real-life inkjet banding defects. Inkjet banding samples were produced by simulating a type of actual inkjet print banding with a high quality proofing system. We simulated bandings at five different frequencies and various contrast levels and at a gray level corresponding to 25% pixel coverage. Fifty observers participated in a visibility and objectionability test with no restriction to view distances under normal office lighting condition and under special lighting for critical proofing viewing. The results obtained show lower threshold values in comparison to reported results on sinusoidal bandings.