The experiment was conducted in a dimly illuminated room. Stimuli were displayed on a 40.0 × 30.0 cm CRT monitor (Sony G520; 85 Hz, resolution of 1,600 × 1,200 pixels) with self-programmed Matlab functions (Mathworks Inc.) using the Psychophysics toolbox (Brainard, 1997 (link)). Stimuli were displayed using an NVIDIA Quadro K600 graphics system and viewed binocularly. To avoid local cues for vertical/horizontal and position, the screen was delimited by a 30.0 cm diameter circular window cut in a black cardboard (Tzvetanov, 2012 (link)). Luminance values were obtained with the help of the contrast box switcher (Li et al., 2003 (link)), that allowed to extend luminance range digitization above 10 bits, and thus provided the necessary minimum contrast step for CSF measure. Calibration was performed each day.
The eye-to-screen distance was maintained with a chin rest and fixed at 4 meters for CSF measure and the experiments for TI test with high-SF, and 2 m for TI test at low-SF. Experiments were initiated by subjects with a keyboard press. Subjects were requested to fixate on a small black square on the screen center and stimuli would be presented 200 ms after fixation point disappearance. Subjects responded by pressing corresponding keyboard keys.
The eye-to-screen distance was maintained with a chin rest and fixed at 4 meters for CSF measure and the experiments for TI test with high-SF, and 2 m for TI test at low-SF. Experiments were initiated by subjects with a keyboard press. Subjects were requested to fixate on a small black square on the screen center and stimuli would be presented 200 ms after fixation point disappearance. Subjects responded by pressing corresponding keyboard keys.
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