FPS (Frames Per Second) is the number of consecutive images captured by a CCTV camera that are used to form the recorded video.
The human brain can process approximately 12 separate images per second so any additional images sent during that second will create the illusion of fluid motion. Therefore by adding 1 additional image to each perceivable image we arrive at 24 frames to achieve what will be perceived as completely fluid motion.
The PAL video format selected 25 FPS as the standard for motion display and this is referred to by CCTV manufacturers as real time due to it being the point that motion appears to flow as it would be really expected to.
Most recorders can record a number of overall frames per second which is then divided between the number of available cameras up to a maximum of 25 FPS each.
For example an entry level recorder may offer 100 FPS across 4, 8 or 16 channel versions of the unit. The 4 channel unit could therefore record each camera at 25 FPS but the 8 channel would be limited to 12 FPS if all channels were in use and the 16 only 6 FPS.
Higher specification recorders will offer up to 400 FPS meaning real time can be achieved across all 16 cameras simultaneously.
They may however only offer real time recording at lower quality settings due to the processing power limitations of the recorder. It is recommended that when selecting a recorder that is carefully examined to achieve the recoding quality and frame rate.
FPS can be set per camera on most professional recorders allowing your system to be tailored to balance fluid motion with the need to save recording space and increase the available playback time. Many situations only require lower frame rates and can be set up accordingly.
This will be considered along with many other factors when designing and planning a CCTV system.