Although the Bergmann/Helmholz Law is well known to every student of visual science, until relatively recently there was little evidence that the law actually applies to human vision. That is, there was little evidence that the tell-tale signs of aliasing accompanied the end of visual resolution as we know it.

In the absence of compelling evidence that neural undersampling actually occurs, a competing theory rose to prominence which proposed that the sampling limit was never attained in 'real life' because spatial filtering by the eye's optical system and and by neural receptive fields attenuates high frequencies, thus preventing aliasing. This is the model illustrated at the right. Notice how the checks of the tweed coat have vanished altogether as filtering reduces their contrast to below our visual threshold. This is the familiar experience we all share in central vision: fine patterns disappear rather than mutate into coarse, aliased patterns which remain visible.

A formal description of this filtering model of the limit to resolution is shown next.

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WWWaveTM 1996
World Wide Web automated virtual environment TM 1996
Kevin Haggerty, Indiana University.