Scan chain faults that affect the scan logic of a design are important to diagnose. However, scan chain faults create large volumes of fail data that make it necessary to terminate the fail data collection process early. An approach to test generation called transparent-scan was shown to have several advantages for diagnosis of scan chain faults over conventional scan-based tests. One of these advantages is that it allows compact test sequences to be generated. This reduces the volume of fail data that scan chain faults produce. The goal of this paper is to reduce the volume of fail data further, beyond test compaction. The paper observes that different clock cycles of the transparent-scan sequence produce similar diagnostic information. Consequently, it is sufficient to store fail data for a subset of the clock cycles of the sequence. A procedure for selecting these clock cycles is described in this paper. Experimental results are presented for a basic and a more comprehensive set of scan chain faults.