hello, There are two steps of filtering in Illumnia : one the chastity filter which determines the read clusters that can be successfully sequenced and another filter which says which reads are failed during Bustard base calling. In my opinion Bustard ( the process of base calling is the sequencing itself which tells us the intensity of the noticed base is valid enough to be added to our sequence or not) also determines the process of sequencing so there should not be any differences between it and the chastity filtering which also determines the validity of sequencing. Am I right? Thanks a lot in advance Narges