Perception, 1977, volume 6, pages 233-234
A wartime anticipation of random-dot stereograms
B Babington Smith Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, England Received 27 September 1976
The stereoscopic pair of photographs reproduced herewith illustrate an unexpected effect, which is not too difficult to account for and contributes to the argument whether the effect of solidity experienced in viewing such pairs is due to expectations of solidity and depth with familiar objects. For maximum effect, the photographs should be looked at stereoscopically before the rest of this note is read. The photographs were taken over Cologne in December 1940 by a photographic Spitfire of the RAF. First viewing of them produced exclamations of surprise and amusement, and they were dubbed 'the Empty Rhine'. Closer investigation showed that the aircraft had been flying downstream and that blocks of ice floating on the surface of the river had drifted between successive photographs, producing parallax relative to the banks and bridges, similar to that which could have been produced by stationary objects at varying distances below the surface. Other points noticeable under a stereoscope are that the apparent distances of the ice blocks appear to increase very rapidly from just outside the moored barges and remain more or less uniform across the breadth of the river. The 'bed' of the river, however, does not
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appear altogether flat; in particular one can see 'ridges' where the ice moved more slowly below the piers of the bridges. The shadows of the bridges on the surface of the river appear suspended in mid air, because they remained stationary while the ice drifted. The photographs seem to be relevant to the controversy which led to Julesz's (1964) work and random-dot stereograms, and are of interest because the pattern of ice blocks has a similar quality of 'randomness'. It is difficult to maintain that the shape of the 'empty riverbed' revealed is something induced or favoured by expectation or familiarity. It is a pleasure to be able to produce with the permission of the Ministry of Defence this early example of a random-dot stereogram. Reference Julesz B, 1964 Science 145 356-362
p
©1977 a Pion publication printed in Great Britain
A wartime anticipation of random-dot stereograms
B Babington Smith Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, England Received 27 September 1976
The stereoscopic pair of photographs reproduced herewith illustrate an unexpected effect, which is not too difficult to account for and contributes to the argument whether the effect of solidity experienced in viewing such pairs is due to expectations of solidity and depth with familiar objects. For maximum effect, the photographs should be looked at stereoscopically before the rest of this note is read. The photographs were taken over Cologne in December 1940 by a photographic Spitfire of the RAF. First viewing of them produced exclamations of surprise and amusement, and they were dubbed 'the Empty Rhine'. Closer investigation showed that the aircraft had been flying downstream and that blocks of ice floating on the surface of the river had drifted between successive photographs, producing parallax relative to the banks and bridges, similar to that which could have been produced by stationary objects at varying distances below the surface. Other points noticeable under a stereoscope are that the apparent distances of the ice blocks appear to increase very rapidly from just outside the moored barges and remain more or less uniform across the breadth of the river. The 'bed' of the river, however, does not
234
B Babington Smith
appear altogether flat; in particular one can see 'ridges' where the ice moved more slowly below the piers of the bridges. The shadows of the bridges on the surface of the river appear suspended in mid air, because they remained stationary while the ice drifted. The photographs seem to be relevant to the controversy which led to Julesz's (1964) work and random-dot stereograms, and are of interest because the pattern of ice blocks has a similar quality of 'randomness'. It is difficult to maintain that the shape of the 'empty riverbed' revealed is something induced or favoured by expectation or familiarity. It is a pleasure to be able to produce with the permission of the Ministry of Defence this early example of a random-dot stereogram. Reference Julesz B, 1964 Science 145 356-362
p
©1977 a Pion publication printed in Great Britain
