09-07-2020, 08:59 AM
It is important to choose a background color of the calibration, validation, and drift check screens that matches the overall luminance / background color of the stimulus Display screens. So if presenting targets / images on a white background during the experiment, use a white background during calibration, validation, and drift checks. Drastic changes in the luminance of the screen (dark to light or vice versa) may cause changes in Pupil size which can introduce drift in the reported gaze location. If the experimental stimuli vary in their overall luminance (as with full-screen natural images for example) then choose a mid-grey as the background color for calibration.