Why are my HEVC (h.265) recordings larger than my AVC (h.264) recordings?

The HEVC codec (h.265) is designed to capture identical video quality at half the bitrate compared to its predecessor, AVC (h.264).  Keep in mind, however, that FiLMiC Pro’s dynamic bitrate implementation operates somewhat independently of these two compression standards.  In other words, selecting HEVC in FiLMiC Pro will not directly reduce the size of your FiLMiC Pro recordings.

FiLMiC Pro users have the option of selecting lower bitrate settings in combination with HEVC.  In theory, this will generate a smaller file size of comparable video quality to that of an AVC recording that was captured using a higher bitrate setting. For instance, a 4k/HEVC capture using the “FiLMiC Quality” bitrate setting will theoretically have comparable, or better quality than that of a 4k/AVC recording using the “FiLMiC Extreme” bitrate setting. 
Please note: While HEVC has its advantages, AVC remains to be a more compatible standard with most operating systems and video editing software.  For this reason, FiLMiC Pro utilizes AVC (h.264) by default, and many FiLMiC Pro users find it most effective stick with the older codec whenever possible.