Motion Blur, light trails

#1

Hi,

I have some video footage of oncoming cars, in the evening. I would like to motion blur this footage but preserve the apparent intensities of the headlights, creating light streaks. What is a good strategy to do this with video footage?

Below are two versions of a still frame. One with “CC Force Motion Blur” and one with no effect, You can see that the light streak from the headlight has dimmed considerably. Can convincing bright light streaks be accomplished with Real Smart Motion blur or other effects/plugins?

By the way, the AE project is set to 32 bits, but of course this is standard 8 bit video from a Canon DSLR.

#2

I would probably try precomposing the footage and adding an adjustment layer with a glow, masking it off to just cover the headlights.

Then in the main comp I would add the force blur.

Might be worth a try?

#3

Yes that is an approach I might try, thanks. I have toyed with some things similar, without much success.

After Effects already has a solution for this problem, I think, but I am not sure if it is implemented for any “forced motion blur” tools out there. If you use lens blur you will know what I am talking about. Lens Blur has a specular brightness option, and a threshold, which allows you to choose a range of brightness to boost. This simulates the effect of a high bit depth image.

Is there not an equivalent tool for motion blur?

ABOVE: Example of AE Lens Blur with the specular brightness cranked to 60 and the threshold at .9

AE Lens Blur, specular brightness 0

#4

You could track a shape to your headlights that is brighter than 1. Turn on the layer’s motion blur and you should get some nice streaks.

#5

Thanks. Both good ideas, and they both work well with a bit of tweaking.

But anyway heads up to any After Effects plugin developers out there, forced motion blur with some sort of threshold glow might be a nice one.

The only problem I have not figured out yet is the streaks seem to precede the blurred cars, or streak across the frame, as opposed to leaving a trail after the light hits a particular spot on the plate, as real streaks do.

#6

Just stumbled across this cool little post. Might be relevant to what you’re looking for.

http://www.videocopilot.net/forum/viewtopic.php?f=33&t=21358

#7

Try adjusting Shutter Phase under Composition Settings -> Advanced. Negative values should bring the blur closer to where you want it.

#8

Also crank up the samples per frame to get smoother streaks.

#9

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