Vsg 2 5

In this study, we applied the CCT 2.0 version (Cambridge Research Systems, Rochester, UK) and a visual stimulus generator (VSG 2/5; Cambridge Research Systems, Rochester, UK) LG with gamma correction and made with a Color Call photometer (Cambridge Research Systems, Rochester, UK). The test was performed in a dark room binocularly at a distance of 300 cm from the monitor. The Forced Choice method was used with four alternatives (Andrade et al., 2018 ), starting the excursion at a specific point in the 1976 International Commission on Illumination diagram (Geller & Hudnell, 1997 (link)) and extending to the center of the color, U'V' space (.197, .469, Costa et al., 2012 (link)). Each participant responded with the answer box, the orientation of the chromatic stimulus in the form of C, moving it up, down, to the right, or to the left. For each correct response, the background chromaticity approached the chromaticity of target C (ranging from 5.7 to 2.8 mm in diameter) and for each incorrect response, the chromaticity of both was spaced apart. The absence of a response was considered incorrect and the test was completed when 11 reversals were performed for each axis tested and the contrast threshold was defined after the last six reversals (Lima et al., 2011 (link)).

Stimuli were created using the ViSaGe and VSG2/5 cards manufactured by Cambridge Research Systems. A 22-in. CRT monitor with a refresh rate of 100 Hz and a display resolution of 800 by 600 pixels was used to present the visual stimuli. Observers sat at a distance of 1 m from the display. To restrict head movements of the observer, a head/chin rest was used.