The CBK55F2K from Sony is a 2K Optical Low Pass Filter for Sony's PMWF5 & PMWF55 Cinealta 4K HD professional camcorders. Low pass filters in front of a camera's sensor helps to prevent moiré artifacts on images.
Optimized to improve image quality of 2K High Frame Rate Recordings
Advanced filter” not a “must have filter” for HFR shooting
Yields “softer, organic images” when shooting 4K high resolution images
Reduces motion-judder. By using this filter, this phenomenon is reduced.