Firm foundation in the main hci principles, the book provides a working

Figure 3.6 A user viewing a display system. The shaded area illustrates the horizontal field of 
view (shown to be much less than the actual for illustration purpose), while the dashed line is the 
same as offered by the display. The display offers different fields of view depending on the viewing 
distance (dotted line in the middle). The oval shape in the display represents the approximate area 
for which high details are perceived through the corresponding foveal area in the user eyes.

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H U M A N – C O M P U T E R I N T E R A C T I O N 
3.2.1.2 Detail and Peripheral Vision 
The human eye contains two types 
of cells that react to light intensities in different ways. The cones, which 
are responsible for color and detail recognition, are distributed heav-
ily in the center of the retina (back of the eyeball), which subtends 
about 5° in the human FOV and roughly establishes the area of focus. 
The oval region in Figure 3.6 shows the corresponding region in the 
display for which details can be perceived through these cells. On 
the other hand, the rods are distributed mainly in the periphery of 
the retina and are responsible for motion detection and less detailed 
peripheral vision. While details may not be sensed, the rods contrib-
ute to our awareness of the surrounding environment.
Differently from that of human perception, most displays have 
uniform resolution. However, if the object details can be adjusted 
depending on where the user is looking or based on what the user 
may be interested in (Figure 3.8a), the overall rendering of the image 
can be made more economical or to doubly emphasize certain objects 
relative to others in their neighborhood (e.g., detail contrast). We may 
assess the utility of a large, very-high-resolution display system such as 
the one shown in Figure 3.9. From a nominal viewing distance, only 
Viewing location (average)
Viewing
distance
(average)
Display size
Smallest
perceivable pixel
(determined by
visual acuity)