![]() Try to equate the background luminance with the mean of the checkerboard (blurring the image helps, ideally the checkerboard vanishes). Ticking the ‘γ’ (gamma) checkbox, and a central checkerboard appears on a grey background, whose luminance is controlled by the slider. Gamma calibrationįor more quantitative assessment, the luminance linearity of your screen should be calibrated. The illusion still occurs! This makes it easier to study it quantitatively, and the modifications described above are all applicable. ![]() By selecting the 20%♴0% entry, the colours are replaced by grey levels of ≈equal luminance. colour, with values taken from Kitaoka’s original picture. The pop-up menu is initially set to Orig. This observation plays a role in our new simple computational model (2020, see below). the center of a disk, and notice that after on- or offset there is a brief seeming rotation of opposite direction. In this mode, you can fixate anywhere, e.g. Tick the checkbox and notice that the picture alternates between full and very low contrast. allows to observe the effect of temporal contrast modulation with variable speed. With onset/offset, no eye movements necessary I find this effect very strong: while the global aspects of the two variants (with and w/o Illusion) are very similar, the loss of motion is striking in the second case.Ĭorrection: in this mode, there still is some illusion, but a different one, as first noted by George Mather: A slight shimmering, somewhat alike to Enigma or Op-Art likely related to microsaccades. The asymmetric sequence requires 6 steps, the symmetric one 4 steps. This can be tested with the checkbox Illusion. When the asymmetric sequence is replaced by a symmetric one, namely …black-blue-yellow-white-yellow-blue-black…, the illusion vanishes. The perceived motion direction is from the black stripe towards the neighbouring dark grey one (or from the white to the neighbouring light grey). If this sequence is reversed (between wheels) using the checkbox Alternate, the seeming motion changes its direction. Element sequence and seeming motion directionĪs detailed on the previous page, this motion illusion requires an asymmetric sequence of the individual elements (wedges), e.g. The arrangement is a simplified version of Kitaoka’s original that allows me to control colour and luminance of the elements, which are now small wedges. If I watch this for an extended time span, the illusion tends to weaken. The top left and right “snake wheels” should appear to rotate clockwise, the top center one counter-clockwise, especially if you’re not fixating them. Use high display brightness for stronger effect. When looking around the above static image you might see illusory rotation.
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