The Role of Motion Blur
Let’s do a deep dive with the new Motion Blur feature, which helps create more natural motion in your video renders. Motion blur is an important part of creating convincing-looking animations, and can even be taken advantage of to render in-action still images.
How Motion Blur Works
Motion Blur can be enabled in the Camera object properties and works by averaging multiple frames together. The feature automatically reduces rendering samples proportionally to blur samples, which means that render times should not be affected. In other words, Motion Blur is free!
Note: Motion Blur is on final render only; it can not currently be previewed in the viewport.
Shutter Speed Settings
Adjust the shutter speed dial to determine the amount of blur, defined by fractions of a second. Smaller numbers (slower shutter speeds) will produce a more exaggerated blur. Generally speaking, a shutter speed twice as fast as the frame rate will produce natural blur. This means for 24 and 30 FPS, you would want to use 1/50 and 1/60 respectively. Using a faster shutter speed may be appropriate for scenes with fast action and using slower shutter speeds can produce a dream-like appearance.
Here is a range of renders showing the differences in shutter speed values. The lower the shutter speed count, the more exaggerated the blur can be.
Adjusting the Samples
The Samples setting determines how many frames are averaged to create the blur effect. For slower shutter speeds and fast motion, a higher sample count will reduce banding artifacts. 16-32x samples work well for most cases. Increasing the Samples setting will not lengthen the render time in most cases, however, if you’re using fewer render samples than blur samples, the render sample count will automatically be increased to match the blur count.
For instance, if your render samples are set to 16x and blur to 32x, enabling Motion Blur will bump up the render sample count and increase render time by roughly 2x.