In previous posts in the series we have looked at reproducing an illusion (see Appendix). Whilst the original illusion was not reproduced there were a few interesting learning points along the way. The effects were very subtle and modifying the brightness and other variables didn’t impact too significantly on these effects. After watching the video below it became immediately obvious that the image developed in the previous posts could be modified to produce a convincing illusion. By inserting the words ‘contrast’ and ‘illusion’ into the circle above the reader may be convinced that the letters at the end of the words appear lighter than the letters at the beginning of the words. All the letters are of course of a similar colour and the effect results from the contrast with the background which is graded.
The contrast effect may be explained by firing in a subgroup of Ganglion cells at the stage of retinal processing as discussed in the talk by Professor Markus Meister below.
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