Purchase this article with an account.
BT Barrett, PV McGraw, P Morrill; Perceived Contrast Following Adaptation: The Role of Spatial Frequency & Stimulus Visibility . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2840.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: It has been suggested that, under certain conditions, orthogonally oriented test gratings show a greater reduction in perceived contrast than those oriented parallel to the adapting stimulus. In the present experiments, we compare the reduction in perceived contrast of test gratings with different orientations following adaptation to a grating with a fixed orientation. Methods: Using a contrast matching procedure we measured the perceived contrast of test gratings oriented at 45° and 135° following adaptation to a 45° grating of the same spatial frequency. Two experiments were carried out. Experiment 1: The perceived contrast of test gratings ranging in contrast from 1 to 0.45 was measured following adaptation to a grating with a contrast of 0.8. This was carried out at two spatial frequencies (2.25, 9 c/deg). Experiment 2: The effects of adaptation upon perceived contrast were assessed for a number of adapting contrasts. A fixed ratio was maintained between the contrasts of the adapting and test gratings (1.33), and a range of spatial frequencies was investigated (2.25-9c/deg). Results: Experiment 1: The pattern of perceived contrast loss for the parallel and orthogonal conditions was very different for the high and low spatial frequency conditions. At the lower spatial frequency, the perceived contrast of the highest contrast test grating was reduced more for orthogonal adapting and test stimuli. This was not observed at the higher spatial frequency. Experiment 2: When the adapting stimulus was low in contrast, its effect was greatest upon parallel test gratings. However, when the adapting stimulus was high in contrast, its effect was greatest on test gratings orthogonal to the adapting stimulus. The contrast level above which orthogonal gratings showed more loss in perceived contrast than parallel gratings was found to increase with spatial frequency, suggesting that visibility of the adapting stimulus is the key to whether this effect is observed. Conclusion: Test gratings oriented orthogonal to an adapting grating can have a lower perceived contrast than parallel gratings of the same physical contrast provided the visibility of the adapting stimulus is high enough.
This PDF is available to Subscribers Only