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gross trends in luminance (e.g. Fig. 11.2) to multiple levels of luminance
(Fig. 11.1), fine profile detail (Fig. 11.3) and surface texture. The aim of this
chapter is to present a survey of laboratory data which shed some light on this
problem of target structure. These data will be considered in terms of the
contour modelling of threshold of Chapter 7 where appropriate. From the
findings the possibilities of extending modelling to cover certain forms of simple
recognition will be considered.
12.1 The annulus / disc experiment
12.2 The multi-contrast experiment
12.3 Contrast sensitivity and the Mach effect
12.4 Complex periodic patterns
12.5 Brightness illusions
12.6 Modelling of simple recognition
12.7 The effect of texture
References
13. BACKGROUND STRUCTURE
As stated in Chapter 11, there are many forms of background structure and
several ways in which they can influence detectability of a target. The structure
may be adjacent high contrast objects which modify thresholds due to their
energy content; local background structure which interacts with the target
destroying the concept of one contrast or one illuminance gradient around a
contour; a local region of dissimilar luminance to the rest of the field against
which to view a target; a sub-threshold structure which nevertheless interacts
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