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Applying the TimeBlur Filter

When a fast-moving subject is recorded on film or video, its edges appear to smear as a result of the object's movement while the shutter is open. The longer the shutter remains open at each frame interval, the more obvious this effect. TimeBlur simulates this phenomenon by sampling its input at "divisions" times over "shutter" frames starting at the current frame plus "offset".

Time blur is commonly applied to garbage masks that are tracked to a fast moving feature. The time blur averages the incoming mask image over the shutter period, to better match the motion blur in the original image and creating a more convincing integration.

TIP:  You can also use the Roto and RotoPaint Global Blur controls to achieve the same results. See Adding Motion Blur for more information on Roto and RotoPaint motion blur.

Applying Motion Blur to a Clip

To apply motion blur to a clip:

1.   Click Time > TimeBlur to insert a TimeBlur node into your script. Place it downstream from the element to which you want to apply motion blur.
2.   In the TimeBlur properties panel, set divisions to the number of times you want to sample the input over the shutter time. For images with fast-moving content higher values are necessary to eliminate "steppiness" or banding in the output.
3.   Set shutter to equal the span of time (in frames) over which the input should be sampled. A shutter time of .5 is typical and would correspond with a camera shutter of 180 degrees.
4.   Set the shutteroffset to control when the sampling of the input starts relative to the frame being rendered, analogous to when the camera shutter opened to capture corresponding film or video footage you might have at the same frame. You may need to adjust this by eye to align, for example, a garbage mask with an underlying feature.

TIP:  You may find that using TimeBlur on all the upstream nodes in your composition can be unnecessary and very time consuming. In these cases, you can use NoTimeBlur node to limit the number of nodes to which you’re applying TimeBlur. Just insert the NoTimeBlur node in your node tree above the TimeBlur and any nodes you want the TimeBlur node to process.