LUCI's ETC uses transmission data of all filters measured by the manufacturer [BARR]. The additional numbers are the identifiers for the filters.
They are stored in wavelength steps of
0.5 nm as well as the previous wavelength-dependent datasets. The transmission curves of these broadband filters are shown in Figure 4. All available filters (including the narrowband filters) are shown in Appendix A.
The optical filters U, B, V, R and I can be chosen for the input of the object's magnitude only. They are originally described in steps of
10 nm (U) and
20 nm (B, V, R and I) [FIL-HP]. By linear interpolation the sampling was increased to
Broadband filters used by LUCI