The Perception of High Frame Rate Videos: Why They Often Seem Unnatural
Why do videos shot at high frame rates, such as 60 or 120 frames per second (fps), often appear as if they were low-budget home videos in the eyes of viewers? It's a question that has puzzled many, but the answer is not as mysterious as it might seem. In this article, we explore how human perception and conditioning play a pivotal role in how we perceive video quality.
Perceptual Conditioning and High Frame Rates
Perceptual conditioning is a powerful force that influences how we interpret visual information. For most of us, videos with a frame rate of 30fps or higher are what we typically associate with video content, while 24fps is more commonly associated with movies. This conditioning has been ingrained in us since childhood, thanks to the prevalence of 30fps and 24fps content across traditional broadcast and streaming platforms.
Back in the 1990s, Kodak attempted to push filmmakers to shoot at 30fps instead of the conventional 24fps. Their rationale? It would make film more “natural” and thus boost sales of their color negative film. However, the move never caught on, as viewers found it unnatural and reminiscent of video quality, which led to the term "soap opera effect."
Digital Cinematography and Frame Rates
The advent of digital cinematography marked a significant shift in how videos are captured and perceived. The frame rate was one of the key factors driving the adoption of digital cameras in the early 2000s. 24p digital, even in standard definition, was transformative, providing a more realistic and cinematic look. HD video, with its 60 or 120fps capabilities, further increased the detail and fluidity of motion, but it also pushed the limits of what our perception can handle.
Human Perception and Frame Rates
Our eyes and brains are finely tuned to process visual information within a certain range. Most experts agree that the human perception of motion is generally accurate within the range of 30 to 60fps. Beyond this range, the additional frames can introduce a level of unnaturalness, especially when viewed on modern high-definition screens.
When videos with a higher frame rate are viewed on a TV or monitor designed for high frame rates, the result is often described as the "soap opera effect." This term is derived from the way TV soap operas, often filmed at higher frame rates, appear hyper-real and sometimes unnatural. To counter this, many feature films shot with high frame rates include a bit of artificial motion blur in post-production, particularly during fast action scenes, to make the motion more natural and blend in digital effects.
Upscaling and Frame Interpolation
Modern TVs and devices often attempt to upscale content to higher frame rates. This upscaling can include artificial intelligence algorithms that interpolate frames, predicting the content between two known frames. While this can enhance the visual quality, the brain may still detect subtle discrepancies, leading to a disorienting picture quality.
It's important to note that my understanding of these concepts comes from extensive reading and discussions with professionals in the motion picture industry. However, I am not an expert myself. If any professionals reading this have corrections or additional insights, I welcome any feedback.
In conclusion, the perception of high frame rate videos is deeply influenced by our perceptual conditioning and the natural limits of human perception. While high frame rates offer potential for improved visual quality, they can also introduce an unnatural look that may confuse or disorient viewers. Understanding these nuances can help in creating more compelling and natural-looking video content.