In the printing process, geometric optical illusions often appear, affecting the perception of shapes by observers. Under the influence of various geometric structures, visual illusions may occur that distort the perception of geometric properties as seen by the observer. This paper presents the results of a psychophysical visual experiment in which three different achromatic variants of the Ebbinghaus illusion with white and black circles were tested. The aim was to investigate how this illusion depends on the coloring of the outer and inner Ebbinghaus circles in printed materials. Samples were defined with white circles, black circles, and black inner with white outer circles. The study involved 27 participants of different genders, aged 18 to 23 years. Differences in illusion strength across samples were tested using the non-parametric Friedman ANOVA for repeated measures, followed by post-hoc analysis with Wilcoxon matched-pairs tests. It was found that filling the circle surfaces with black significantly affected the strength of the illusion (p < 0.05). The highest intensity was observed in samples with colored inner and outer circles.
Budimi et al. (Thu,) studied this question.