Biology Reference
In-Depth Information
550 nm
4
3
2
1
0
10
20
Time in dark (minutes)
30
Fig. 9.1 Absolute (●) and specific-hue (Δ) thresholds of a 550 nm light (the
absolute light and colour thresholds) measured at 7° extrafoveally during
long-term dark adaptation. The test field was 1 × 1° exposed for 0.5 s.
aware of the light and colour of the test stimulus when the test
intensity is increased from below) coincided for red, green and blue
test lights. But thereafter, during the second phase of dark adaptation
where only rods increased their sensitivity, the specific-hue threshold
started to rise markedly for all the test colours. The rise was most
pronounced for the blue and least for the red test colour. Presuming,
in accord with Schultze and Parinaud, that rods mediated achromatic
vision only, he explained the rise of the speciic-hue threshold
obtained simply by the increase in rod sensitivity.