Peripheral vision and pattern recognition: a review - strasburger - main

Peripheral_Vision.doc
We finish this brief historical overview with three psychophysical papers. Anstis (1974) helped
to popularize phenomena of indirect vision by providing demonstration charts that nicely capture
some essentials. Figure 7 shows peripheral letter acuity. Compare this chart with his
demonstration of crowding from the same paper which is shown in Figure 19 in Chapter 5. The
complementary approach for characterizing the visual field is by measuring luminance
increment (or contrast) thresholds. Harvey and Pöppel (1972) presented detailed perimetry data
(Figure 8a) and derived a schematic characterization of the visual field with respect to sensitivity
(Pöppel & Harvey, 1973). The interesting point is that isopters are isotropic in the center part of
the field but elongated horizontally further out. At the transition, there is a performance plateau
on the horizontal, but not on the vertical meridian (Figure 8b). We will come back to this in
Section 4.2.
Figure 7. Demonstration of
peripheral letter acuity by Anstis
(1974) (cut-out). Letter sizes are
chosen such that they are at the
size threshold (2 sj’s, 216 cd/m²)
during central fixation.
Surprisingly, this is true almost
regardless of viewing distance, as
eccentricity angle and viewing
angle vary proportionally with
viewing distance. (To obtain the
chart in original size, enlarge it
such that the center of the lower
“R” is 66 mm from the fixation
point).
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