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Seiichiro Naito, Naoko Kato; Plasmid illusion : symmetrical composition for equiluminance condition. Journal of Vision 2007;7(9):455. doi: 10.1167/7.9.455.
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© ARVO (1962-2015); The Authors (2016-present)
A new illusion figure named Plasmid illusion (PI) is created. The advantage of PI is that the figure elements are arranged in symmetrical positions with respect to the center point so that they easily yield the equiluminance condition if a subject fixates at the center. We obtained clear reduction of the magnitude of illusion at equiluminance condition. The illusion was diminished to 20%. In general, some classical illusions lose the illusory effects at equiluminance condition and others do not. One of the typical examples for the latter would be Gravity lens illusion (GLI). We failed to find the equiluminance condition for GLI to reduce the illusory effect, even though we tried not only red-green colors but also light-blue-gray-yellow color combinations. The illusion persisted with the effect perfectly. One of the reasons for the no-reduction would be the difference of the equiluminace condition over different eccentricities. By preliminary measurements, we also found that the difference of the equiluminance condition between the fovea and some peripheral areas at around 10 degrees was more than 20%. The difference is far above the magno sensitivity. Therefore we draw a red ring on a gray background and put 4 white tiny test segments on the ring at symmetrical positions. Then we add 4 pieces of green inducing ring segments on the flank of the 4 test segments in opposite directions so that a pair has inward inducing ring segments and the other pair has outward segments. The test pair with inward segments looks closer and the other looks far. The PI is a variant of GLI. The inducing figures of GLI are arranged at highly distorted quadrilateral, while the inducing segments of PI are fit into the ring. The luminance of green is changed. The appearance of PI is similar to plasmids in biology.
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