Eye-tracking technology: Understanding what we really see

This post was contributed by Guy Collender from Birkbeck’s Department of External Relations.

Our eyes are imperfect, but we don’t notice their limitations. This reality and its implications for artists and film-makers were clearly shown during a Science Week lecture at Birkbeck.

There was audience participation too, as the eye movements of volunteers were tracked with high-speed infrared cameras to prove what happens when people look at pictures and films.

Dr Tim Smith, of the Department of Psychological Sciences at Birkbeck, shared his research during the talk, including his work with Tate Britain to help restore a famous painting.

He began his talk on Wednesday 29 March by outlining the theory of vision science – the study of how people view, perceive and remember visual scenes, and how this influences their actions.

In practice, our eyes often fail to detect changes in the background because they can only focus on a small proportion of the visual field and process a limited amount of information. This “phenomenon of change blindness” is significant as it means viewers can be distracted from what is happening. Smith said: “What we think we see is rarely actually what we see.”

A masterpiece restored

Destruction of Pompeii and Herculaneum by John Martin

Destruction of Pompeii and Herculaneum by John Martin

Art and science are often closely linked, and Smith demonstrated how he has applied insights from vision science to inform art conservation.

In 2010, Tate Britain decided to attempt a restoration of the flood-damaged 19th century masterpiece Destruction of Pompeii and Herculaneum by John Martin. A large section of the dramatic painting, which documents the eruption of Mount Vesuvius, was lost, and Smith was asked for his expertise to recommend how to remedy this. He used eye-tracking equipment to assess how viewers would look at four prototypes of restored versions of the painting: fully restored, restored but with less detail in the filled section, muted colour in the filled section, or a neutrally coloured infill.

His findings showed that the eyes of viewers were drawn to the edges of the lost section when it was filled with a muted or neutral colour, and this detracted from the original intention of the artist as this was where the mouth of the volcano was supposed to be.

Informed by Smith’s research, Tate conservator Sarah Maisey embarked on a reversible reconstruction of the lost section. Some detail was omitted in the reconstructed section, allowing viewers to see the entire main content of the painting while spending most of their time viewing the original sections. The painting was exhibited during the recent John Martin Apocalypse exhibition at Tate Britain, and Smith said the reaction to the restoration was “overwhelmingly positive.”

Cinematic continuity
Smith continued by demonstrating how gaze patterns generated by eye-tracking technology also show how people watch films. He outlined the history of film and editing conventions, and explained how film-makers replicate the way people attend to, and perceive, reality. This includes focusing on motion, helps lead to a seamless representation, and means that edits largely go unnoticed in today’s films, where the average duration of a shot is only 2.5 seconds. Smith added: “If we compose edited sequences according to these conventions, we can make viewers blind to a large proportion of the actual cuts.”


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