## 3 Results and Discussion
### Softbox  
We have tested a range of light-shaping attachments known as softboxes, which differ in size, shape, and material. Their main aim is to widen the light beam, with the reflections on the inner surface passing the reflected light through white material to soften the edges of the light beam. Figure 5 shows that the results for softboxes vary not only from light source to light source, but also between them. Two samples cross the dashed line for the xenon light source, which marks the minimal acceptable difference value. Both results were obtained in combination with a xenon light source and a stripbox light-shaping attachment, with all three extensions (box, liner, and cover) attached. The samples differ only in the orientation of the light-shaping attachment. With horizontal orientation, the average CRI difference is 2.85 lower than the original light source itself, and 2.35 lower when vertical. Negative differences can also be observed with other combinations of xenon light sources and this light-shaping attachment. When the cover or liner is used in combination with the box, the differences are between \(-1.53\) and \(-0.88\). However, when only the box is fitted, the differences are positive regardless of the orientation of the modifier, suggesting that the negative impact on the colour rendering index is due to the interaction of the original light with the liner and/or the cover of the light-shaping attachment. In combination with halogen, the results show more positive and negative deviations, but the negative differences are smaller and can even be neglected as they are between \(-0.17\) and \(-0.12\), similar to the differences observed with snoot. These trends can also be observed in CRI differences for every TCS; Figure 9 shows the largest deviations in results so far. Again, R9 shows the largest differences when coupled with xenon; however, other samples, except R3, R7, and R14, show a distinctive decrease in CRI quality when liner and/or cover are applied to the stripbox. The results for halogen show the largest deviations for samples R10 and R12, which are the only reason for the higher average CRI differences. Figure 8: Influence of beauty dish, gold, silver, or white deflector dish, and added grid on every CRI TCS for (**a**) xenon and (**b**) halogen. These differences indicate that the most likely reason is the interaction between the light source and the materials used for liner and cover, which are manufacturer specific. We analysed and compared the spectral power distributions of the tested light sources in Figure 1 and the reflectance spectra of the liner and cover of the Quadralite stripbox and other modifiers from Elinchrom, shown in Figure 3. A peak around 450 nm, i.e., in the blue part of the visible spectrum, is noticeable in the Quadralite fabric combinations. The peak values are above 100%/nm for both the liner and the cover, namely 109.9%/nm for the liner and 109.5%/nm for the cover, while together they reach 104.1%/nm. Values above 100%/nm in the blue part of the spectrum indicate the use of brighteners, resulting in a higher degree of whiteness of the materials. Whilst this is often a desirable feature of textiles, it leads to poorer results when combined with a xenon light source, whose spectral power distribution also peaks in this part of the spectrum, as shown in Figure 1. This overlap of spectral distributions increases the effect of the brighteners and lowers the average CRI values achieved. However, if this light-shaping attachment is coupled with a halogen light source, the spectra do not overlap and increase the difference, but regulate each other, resulting in smaller or even more favourable differences. To further investigate the influence of softboxes on the CRI of the original light source, in Figure 10 we show the CRI results for each TCS for rectangular softboxes, where the samples differ by the combination of softbox additions (liner, cover, and grid).