Examples of running PCA on the DC21bwbfe/SN2021bnv data (Type Ia SN; r band). We show the instances where the S/N is low (approaching the detection limit), but other features still have high quantiles to assist the candidate selection. At visit 978220, the low S/N is caused by poor weather, and the S/N increases afterwards even though the transient is getting fainter. Here the results are strongly contaminated by noise, and the PCA R/B shows mediocre but acceptable performance. Top: PCA result using 15 features (Table 3, Figure 16). Bottom: PCA result using six features (Figure 17).