What is Frame Rate? — Ultimate Guide to Frames Per Second Explained

At its core, cinema is built upon a fundamental illusion: the illusion of motion. In reality, when we watch a film, we are not seeing true, continuous motion – we are seeing a rapid succession of still images that create the perception of movement.

This illusion is made possible through a principle known as “persistence of vision.” When still images are shown rapidly enough, our brains lose the ability to distinguish the individual frames. Instead, our brains blend these frames together into a single, seamless motion.

The number of individual frames shown within one second is known as the frame rate, expressed in frames per second (fps). For example, a frame rate of 30 fps means that 30 individual frames are displayed every second.

The Standard Cinema Frame Rate: 24 FPS

When sound was first introduced to motion pictures, filmmakers had to find a balance between accommodating sound technology and minimizing the amount of film required. The frame rate of 24 fps emerged as the industry standard, providing a smooth, “cinematic” look while keeping film costs manageable.

This consistent use over decades has cemented 24 fps as the most widely recognized “cinematic” frame rate. However, some notable exceptions have challenged this convention in recent years, such as Peter Jackson’s “The Hobbit” shooting at 48 fps and Ang Lee’s “Gemini Man” at a remarkable 120 fps.

While higher frame rates can create an immersive, lifelike experience, they also require specialized projection equipment to fully appreciate the intended effect. As such, the 24 fps standard remains the most widely adopted frame rate for traditional cinematic presentation.

Creative Frame Rate Manipulation

Beyond the pursuit of realism, filmmakers often deviate from standard frame rates to achieve specific creative effects. Two common techniques are:

Fast Motion (Low Frame Rate)

Shooting at frame rates lower than 24 fps, known as “undercranking,” can create a choppy, jittery aesthetic. This effect is often used to evoke a vintage, home-movie feel or to add a comedic element to a scene.

A variation of this technique is “step printing,” where footage is shot at a low frame rate (e.g., 6 fps) but then duplicated to match the 24 fps playback rate. This creates a streaking, blurred effect that can convey a visceral, subjective perspective.

Slow Motion (High Frame Rate)

To create smooth slow-motion effects, filmmakers “overcrank” the camera, shooting at frame rates higher than the intended 24 fps playback rate. The higher the capture rate (e.g., 48 fps, 120 fps, or even up to 1000 fps), the slower and more detailed the slow-motion effect can be.

Slow motion is often used to emphasize action, emotion, or dramatic moments, making horror more terrifying, action more spectacular, or comedy more hilarious.

Understanding Frame Rate Relationships

When working with frame rates, it’s essential to understand the relationship between the capture rate (the rate at which frames are recorded) and the presentation rate (the rate at which frames are played back).

For normal motion, the capture rate and presentation rate should be equal. However, for creative effects like slow motion or fast motion, these rates must differ.

To achieve slow motion, you would shoot at a higher capture rate than the intended 24 fps presentation rate. Conversely, for fast motion, you would shoot at a lower capture rate (undercrank) compared to the 24 fps presentation rate.

Mixing capture and presentation rates can lead to unintended effects, such as stretched or compressed motion and audio. Therefore, it’s crucial to plan and manage frame rates carefully to achieve the desired aesthetic.

Choosing the Right Frame Rate

Deciding which frame rate to use depends on the desired “quality of motion” – whether you want normal, fast, or slow motion. Here are some general guidelines:

• Normal Motion: Match the capture rate and presentation rate, typically 24 fps for a cinematic look or higher rates (e.g., 60 fps) for smoother motion in high-action scenes.
• Fast Motion: Undercrank the camera by shooting at lower frame rates (e.g., 12 fps or 6 fps) while presenting at 24 fps.
• Slow Motion: Overcrank the camera by shooting at higher frame rates (e.g., 48 fps, 120 fps, or even up to 1000 fps) while presenting at 24 fps.

Remember, your presentation rate ultimately determines how the audience will perceive the motion on screen. Experiment with different frame rates to find the right balance for your project’s creative vision.

Final Thoughts

Frame rate is a powerful tool in a filmmaker’s arsenal, allowing them to manipulate the perception of motion and create unique visual experiences. By understanding the principles of frame rate, capture rate, and presentation rate, you can unlock a world of creative possibilities.

Whether you aim for the classic 24 fps cinematic look, the smoothness of higher frame rates, or the exaggerated effects of fast or slow motion, mastering frame rate will elevate your storytelling and captivate your audience with the illusion of motion.