Performance of the classifier with the most significant PCA components and significance of the PCA components. The bar chart shows the standard deviation in the distribution of the first 20 PCA components across the spectral classes in decreasing importance in the context of Euclid simulations. The orange and green lines represent the performance metrics S and F₁ for classifiers that use only the most “significant” PCA components, as defined in the text, and given leftwards in the bar chart. The dashed lines depict the results of the optimisation.