## 2 Materials and Methods
### Psychophysical Experiment  
For this study, the iPhone XS Max was utilized, a device previously tested using the MDCIM [13]. As an Apple product, it stands out as one of the highest-rated brands in the market, it belongs to the most represented brand among the 11 characterized devices, and has an OLED display. The experiment compared the sRGB color space with the MDCIM based on the average parameters from all Apple devices in the sample, referred to as the CAAD. The test involved visual assessments of 30 low-gloss samples from the NCS Quality Level 2 set. NCS samples are standardized color representations based on the Natural Color System, a scientifically developed model for describing and categorizing colors as perceived by human vision [36; 37]. Unlike systems based on physical color mixing, the NCS is rooted in perceptual attributes, using six elementary color percepts: white, black, red, yellow, green, and blue. Each NCS color is defined by its similarity to these elementary colors, allowing for a highly intuitive and consistent classification. NCS samples are produced under strict quality controls to ensure accurate color rendering across various applications. They are widely used in design, architecture, and color science, and are particularly useful in psychophysical experiments where consistent and reproducible visual stimuli are required. The samples used in this particular experiment included colors from six chromatic categories--yellow, orange, red, purple, blue, and green--with variations in lightness and saturation, and also six achromatic samples, as these have previously been identified as particularly challenging for color reproduction accuracy [23]. The color characteristics of these samples are shown in Figure 2.  
To prepare the samples, their spectral reflectance data were measured using a BYK-Mac multiangle spectrophotometer at 110\({}^{\circ}\) specular angle. This angle minimizes the effects of gloss and produces results comparable to d/8 spectral reflectance data. The visual assessments took place in a light booth, the JUST Normlicht LED Color Viewing Light, under D65 illuminant and 750 lx illumination level (JUST Normlicht, Langhorne, PA, USA). Eight observers (3 males and 5 females, aged between 22 and 25 years) with normal color vision (verified by Ishihara tests) participated. During testing, the iPhone XS Max was placed flat in front of the observers and viewed directly from above. As illustrated in Figure 3, the physical samples were held beside the display for direct comparison, with observers allowed to tilt both slightly for better judgment. The entire experiment was repeated for all 30 samples, with each observer completing three separate sessions. The order and positions of samples were randomized to eliminate repetition bias. As shown in Figure 4a, each displayed image contained two color patches: one generated using the default sRGB method and the other using the CAAD model. The patch positions were also randomized to prevent bias. The color patches were designed to match the dimensions of the physical paint samples (2 cm \(\times\) 5 cm). To mitigate simultaneous contrast effects, the background color of the digital image was adjusted to closely replicate the color of the light booth used during the visual experiment. Although this configuration could introduce minor spatial variations in luminance and potentially alter the SPD, such effects were minimized by consistently positioning the test samples at the center of the screen, where display uniformity in both luminance and chromaticity is typically highest. Display uniformity was verified through both visual inspection and instrumental measurements. Consequently, any influence of the simulated background on the SPD was considered negligible for the purposes of this study. Figure 3: Photograph of the general setup for the psychophysical experiment in the light booth, comparing the physical sample with the displayed color.