**4. Conclusions**

Visual assessments under two light booths differed because of the variation among the light sources' spectral and colorimetric characteristics. We compared an earlier technologybased light booth, which is still used in the textile industry, and which contains illuminant A (Tungsten lamp) with CCT 2700 K, TL84 (tri-band fluorescent tube) with CCT 4000 K, and simulator D65 (CCT 6500 K), with a different light booth, whose original light sources have been replaced by currently available LED retro kits from equivalent CCTs. As an inexperienced customer or industrial user, our question was, how important is this replacement? The results indicated that two different standard lighting technologies with the similar CCTs cannot reproduce the same estimates because the light sources produced different SPDs. It is illustrating that caution is necessary when comparing results obtained from two different light booths. The variability of the light sources' SPDs or the observer or the sample should be modeled considering the light booth's technology to estimate its contribution to the overall variability. The close relationship between perceived and CAM02-UCS suggests that if both booths are used after the light sources have been calibrated, a formula based on color appearance models must be used to predict color appearance. To obtain better agreement between perceived and calculated color difference, one must need to avoid light booths with nominally white light sources.

**Author Contributions:** Conceptualization, M.V. (Michal Vik); Data curation, A.A.M.; Formal analysis, A.A.M.; Investigation, A.A.M.; Methodology, A.A.M. and M.V. (Martina Viková); Software, M.V. (Martina Viková); Supervision, M.V. (Michal Vik) and M.V. (Martina Viková); Visualization, A.A.M.; Writing—original draft, A.A.M.; Writing—review and editing, A.A.M. and M.V. (Martina Viková). All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Technical University of Liberec as part of the Student Grant Competition under the project number SGS-2020-6038, as provided by the Ministry of Education, Youth and Sports of the Czech Republic in the year 2020.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Conflicts of Interest:** No potential conflict of interest was reported by the authors.

### **References**

