In this paper, the impact of the degree of compression by High Efficiency Video Coding (HEVC) on observers ability of detecting certain events in videos obtained by outdoor CCTV cameras is studied. This was done by extensive subjective testing. The testing was performed also for H.264/MPEG-4 Part 10 AVC compression on similar bitrates and the capabilities of detection were compared and thus the superiority of HEVC was proven. Also the threshold for encoder setting, where the increase of bit rate or decrease of quantization parameter (QP) do not improve observers ability to detect the events, was proposed.