Mastering Motion: How Smear Frames Enhance Animation

Let's look at an example from The Simpsons:

Unlike standard frames that might show a clear picture of a character at a specific point in time, a smear frame blurs these distinctions, presenting a visual interpretation of motion that guides the viewer's eye across the screen.

Another example, if you recall the fast-paced antics of characters like Road Runner or Bugs Bunny in classic Looney Tunes, those swift movements are often animated with the help of smear frames to smoothly transition from one point to another within a split second.

Why Animators Use Smear Frames

The most common use of smear frames is to simulate motion blur. This technique mimics the effect created by a camera when capturing fast movement, and it adds a realistic touch to animations. For instance, when an arrow is shot from a bow, a smear frame might depict its flight with a stretched appearance, hinting at its rapid journey across the screen.

While smear frames originated in traditional 2D animation, their impact isn't confined solely to this medium; they are prevalent in 3D animation as well. For example, animators in animated films like "Spider-Man: Into the Spider-Verse" use smear frames to maintain a comic book feel.

Smear frames emphasize an object's motion path, seamlessly blending transitions between poses or actions. Characters performing acrobatics, like somersaults or spinning kicks, often use smear frames to highlight fluidity and grace, capturing the audience's imagination.

Sometimes, multiple frames can be combined into one smear frame to condense action. This is particularly useful in fast sequences to capture critical elements without overwhelming the viewer with too many individual frames.

1. When To Use A Smear Frame

While they inject energy into scenes, their effectiveness relies on strategic placement.

Smear frames are best during rapid movement or transition moments, like a character lunging forward, an item being thrown, or exaggerated comedic actions.

In fighting animations, each swing of the fist or blade is accentuated with a smear frame to portray speed and aggression:

But it's important to maintain consistency—the technique should remain fluid throughout the scene.

Animators also avoid overuse, as excessive smears can clutter visuals and confuse the viewer.

2. Two Smear Frame Techniques

Animators work with a sequence of frames shown in rapid succession. Motion blur is achieved by simulating what happens when the camera's shutter stays open for a duration while capturing multiple positions of a moving object within that single frame.

There are two types of smear frames:

• Elongated in-between - This technique elongates the subject to bridge the gap between key poses over one or two frames. Some animations in Naruto Shippuden are famous for their exaggerated smear frames:

• Multiples - Here, animators duplicate parts or the entirety of the subject along its motion path while adding a slight blur. Here is one from Looney Tunes:

In 2D animation, smear frames rely on stretching, warping, or multiplying elements within a scene. Balance is key to make sure the smears enhance rather than overwhelm the action. 

Modern VFX and photo editing software often include motion blur settings to digitally simulate the smear frame effect via algorithms, giving animators new tools to achieve the desired effect with greater control and efficiency.

Using smear frames in 3D animation involves manipulating the 3D models themselves or through technical effects such as adjusting the mesh. Characters and objects can be stretched or distorted to match the speed and style of 2D smear frames. Animators can also multiply meshes or integrate motion blur to achieve the desired illusion.

3. Movement Breakdown

While smear frames and in-betweening occur during movement breakdown, their roles differ significantly. In-betweening focuses on creating smooth transitions through evenly spaced, accurate frames. Smear frames, on the other hand, are more about exaggerating motion to convey speed and dynamism at key points. Both techniques complement each other: while in-betweening ensures consistency, smear frames add randomness.

During breakdown, the creation of smear frames usually goes as follows:

1. Identify the motion - First, identify the keyframes between which the fast motion occurs. These could be anything from a character throwing a punch to a ball being kicked. Smear frames are particularly useful in actions that need to convey speed.
2. Plan the timing - Determine where the smear should occur in the movement. Smears typically fall between two extremes or key poses in an action. For instance, if a character is quickly turning their head, the smear would occur between the start and end of the head turn.
3. Sketch the smear frame - Begin by sketching the object or character in the distorted state using the techniques mentioned earlier (duplication, stretching, or motion lines).
4. Use exaggeration - Don't be afraid to go over the top with exaggeration. Smear frames are not about realism―but about conveying energy and speed. For example, when animating a character's punch, extend the arm to appear longer than it actually is.
5. In-between frame placement - Place your smear frame between two keyframes. It can be a single frame in a 24 fps animation, just enough to provide a brief glimpse to enhance the motion.
6. Test with timing - Test the animation to see how it flows once your smear frame is in place. Adjust the timing if necessary.

Conclusion

Animators are illusionists, and smear frames are a prime example of this. Smear frames add an illusion of speed by playing a simple trick on our eyes, and the result is memorable.

Unfortunately, this technique is becoming less common with software features to mimic motion blur, but it’s an integral part of what makes vintage, old-school animation great. New animation productions rely on smear frames to give a retro look, or simply to add a sense of surrealism.

If you want more examples of surprising smear frames, check out the r/smearframes subreddit. Note that you can also use video players like VLC Media Player to view videos frame by frame to catch smear frames in the wild.