Springboard, And A Short Aside – The Persistence of Vision

Many sources explain the psychophysical basis of frame based animation in terms of the ‘persistence of vision’ effect, whereby it is claimed that the retina of the eye retains an afterimage of one frame and somehow blends it with the next, thus providing an illusion of continuous motion.

Unfortunately, while this explanation is the one that is typically offered as the mechanism by which we experience the illusion of motion from frame-by-frame animations, it is not the reason that is accepted by cognitive psychologists. (The actual explanation is beyond the scope of this post; you need a proper Cognitive Psychology/Psychology of Perception course for that! maybe something like this? Signals and perception: the science of the senses)

In a short essay entitled “Persistence of Vision”, Stephen Herbert provides a brief history from cinema of how this popular misunderstanding came to be. You can read the article here: Persistence of Vision.

A more comprehensive refutation of the persistence of vision explanation, along with some simple experiments (using animated GIFs ;-) that demonstrate both the actual persistence of vision effect, as well as how it does not account for the illusion of motion, is given by Rod Munday in this ‘lecture’ on The Moving Image. Links to several other academic papers on the subject are also provided.

PS I’ve placed this post in the Springboard category, as well as a couple of other categories. Springboard posts will be light on content, (‘incomplete’ would be another word for it!) but will always link out to one or more hopefully reputable sources, from where you can go on to find out more about a particular topic.

I’ve also categorised it as an Aside, so it’s slightly off the main topic the uncourse…

Please feel free to comment back with anything you find out from following the links that is relevant to the springboard topic. For example, in this case, it might be a summary of how the ‘persistence of vision’ argument came to be proposed and commonly accepted; a review of an experiment that attempts to refute the persistence of vision hypothesis; or an explanation of what is thought to explain our perception of motion from a watching a sequence a fixed images presented at a rate of several images per second.

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