The balancing of primary subject and supporting details is most readily apparent in visual compositions from mediums such as photography and cinematography. The speed of the composition determines the clarity of the overall composition.
In photography and subsequently cinematography, the film speed determines a number of components within a given composition. Most prominently the speed determines the level of detail and clarity of the the piece. The restriction of adjusting the speed at which a composition is captured is that as the speed increases to capture fast subjects with more clarity, the more detail is sacrificed.
The concept of speed and clarity is just as visible in a narrative composition as it is in the visual arts. As the speed of the composition increases, the subject becomes clearer as the focus but the level of detail is reduced as the speed - pacing is increased.
In a narrative the descriptors, dialog tags and even breaks either page or chapter are the equivalent 'film grain' in the piece. Increasing the pace of the narrative makes these elements seem larger and even distorted compared to the piece. The primary subject becomes even clearer but the surrounding details begin to lose detail to keep that pace. While reducing the speed of the piece too much can make the overall composition seem unfocused.
Every composition is a delicate balance of speed and clarity. Increasing the details reduces the focus of the primary subject and slows the pace. Likewise, too little detail yields a fast-paced blur of a composition.