...
With Pass 8, event_types are introduced. Even though these are essentially a generalization of conversion_type (i.e., front vs back converting events) in that the the event types partition the data into distinct subclasses which have their own effective area, point spread, and energy dispersion functions, in Pass 8, there are alternative partitions for a given class. For example, the Pass 8 SOURCE class selection can be partitioned in one of three ways: into front vs back converting events, into events belonging to one of 4 "PSF" subclasses, or into events belonging to one of 4 "EDISP" classes. The Pass 8 event classes and types _class and event_type descriptions and usage are described in the following links.
...