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Preface.
Since first becoming involved in research into the factors which control thresholds of
human visual performance over 25 years ago, I have become more and more fascinated
by the possibilities of computer vision based on human vision. In those early days it was
difficult to confirm how human vision worked or, indeed, how such things as display
characteristics influenced it. Image quality measurement was still largely subjective,
visual physiology and neuro-physiology of primates, as opposed to lower animal vision,
was in relative infancy, colour vision was open to wide speculation and modern
electronic computers, particular digital computers, were also in their infancy. In the
1960's and 1970's I considered myself fortunate, therefore, to have direct and deep
involvement in the development of objective image quality measurement, plus wide
ranging explorations of thresholds of visual performance. At the same time I was
privileged to have close contact with some of the workers involved in the more important
work on visual physiology and neuro-physiology, whilst being kept aware through
colleagues of the developments and advances in electronic computing. As a result, by
the mid 1970's I felt that, although the subject was (and still is) highly controversial, I had
a fairly clear idea of how at least the early stages of human vision worked and how they
interacted with such environmental factors as image quality and display noise. Over the
years I have been acutely aware that my views on, and interpretations of, human visual
function were opposed to those of many others, and often with those of the
'Establishment'. As the studies have progressed I have, therefore, endeavoured to justify
at least the adequacy of my views by practical demonstration. Over the same period, and
up to the present day, I have been delighted to find many new facts and figures
concerning visual function emerging which, by and large, are supportive of my approach.
However, full justification and demonstration of mechanisms of human vision is not the
purpose of this book, and will not be presented, other than in summary and by inference
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