In a previous post, I attempted to create a visual illusion from scratch. Rather than producing a neat visual illusion the main point was to understand a little about how illusions might arise. My rather crude efforts produced the circle above. This is a black circle with white etchings in the circumference producing discontinuities in which it blends in with the background. I was persuaded that a weak movement effect could be discerned when looking at the centre of the circle and diverting the gaze to another fixed point. Furthermore I hypothesised that this might be due to a difference in the way the central and peripheral parts of the vision are processed.
Continuing, I produced the circle below.
In this instance I have created two concentric circles, again quickly etching out the circumferences. I was interested to know if any effect could be gained from combining two circles in this way. I was hoping that by alternating the discontinuities in the inner and outer circles I might effect the illusion of movement. This was not the case, at least when I looked at it. However there was a powerful after-effect when I looked at the image and then diverted my gaze to the an adjacent white space. In this case the image persisted but with the black colouring of the circumference replaced with a ghost like image which persisted for a matter of seconds. The colour was difficult to make out but it looked fluorescent yellow. Along the way I learnt (and hypothesised) a few things
1. The effect depends on the distance from which the image is viewed
2. The effect depends on the size of the image at any given distance
3. Poorly constructed discontinuities detract from the effect
4. The brain quickly perceives irregularities in any patterning which may override a gestalt effect
5. A movement effect may have been more likely with a thinner circumference
Have a look at the second figure and then take a look away at the white background elsewhere. Do you see an after-effect? Try the poll below if you’re interested.
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