2.3. Stimuli
Screen luminance and ambient illuminance were chosen as independent variables. Two levels of screen luminance (Low; High) and two levels of ambient illuminance (Low; High) were selected. As to luminance, contrast ratios were calculated according to the Michelson definition of contrast (Michelson, 1927): [C = (Lmax Lmin)/(Lmax + Lmin)] where C = contrast, Lmax = maximal luminance, Lmin = minimal luminance. By means of a digital luminance meter for contact measurements (Mavo-Monitor; www.gossenphoto.de), we measured luminance for black (Lmin) and white (Lmax) screen for the two experimental conditions (Low, High). For screen luminance, contrast ratios were as follows: Low: C = 0.998 (Lmax: 20 cd/m2 ; Lmin: 0.02 cd/m2). High: C = 0.997 (Lmax: 140 cd/m2 ; Lmin: 0.2 cd/m2). As to illuminance, we measured screen off the amount of light that impacted on participants’ eyes for the two levels of ambient illuminance:
Low: 5 lx.
High: 85 lx.
2.3. StimuliScreen luminance and ambient illuminance were chosen as independent variables. Two levels of screen luminance (Low; High) and two levels of ambient illuminance (Low; High) were selected. As to luminance, contrast ratios were calculated according to the Michelson definition of contrast (Michelson, 1927): [C = (Lmax Lmin)/(Lmax + Lmin)] where C = contrast, Lmax = maximal luminance, Lmin = minimal luminance. By means of a digital luminance meter for contact measurements (Mavo-Monitor; www.gossenphoto.de), we measured luminance for black (Lmin) and white (Lmax) screen for the two experimental conditions (Low, High). For screen luminance, contrast ratios were as follows: Low: C = 0.998 (Lmax: 20 cd/m2 ; Lmin: 0.02 cd/m2). High: C = 0.997 (Lmax: 140 cd/m2 ; Lmin: 0.2 cd/m2). As to illuminance, we measured screen off the amount of light that impacted on participants’ eyes for the two levels of ambient illuminance:Low: 5 lx.High: 85 lx.
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