Join Mark Christiansen for an in-depth discussion in this video Match motion blur: No keyframes, part of After Effects Compositing 03: Advanced Matching and Looks.
Now let's examine, how to use the Pixel Motion Blur effect, to add motion blur to a layer that contains plenty of motion. But that motion isn't being generated by any keyframes in the timeline. Here is a foreground that clearly needs motion blur to match the background car. So Pixel Motion Blur analyzes the motion of actual individual pixels in order to generate motion blur. It's an automated tool, but nonetheless it has definite things you need to watch out for. So let's get right down to it. I will apply Pixel Motion Blur.
It's under the Time menu. And a couple of things instantly happened here. Let's just take a look. First of all, here's color no longer matches. But there is definitely motion blur on him. Now the shift in color is due to the fact that I put Pixel Motion Blur below a Levels effect, and it's cancelled it out. Something you have to watch out for with any effect that's in that Time submenu is that they'll do this. Anything that's shifting the time in the comp sometimes will cancel out effects higher in the stack. The simple solution here is just to move Levels below Pixel Motion Blur, so that it happens afterwards.
And that problem is solved. We can also move Levels into the precomp and that would solve it as well. Now, the length of the motion blur here looks okay. It looks about right actually. And it's using the default Manual shutter which I recommend, don't use Automatic. Set to an angle of 180. That is actually the frame rate used to shoot this background. And since we are now retiming the foreground to match it, the amount of motion blur is correct.
It just looks very steppy and low-quality. I like to set the Shutter Samples to a minimum of 16. And when I do that, you're going to see all those little striations and steps go away. You can go higher if you want, it will just slow things down. I don't usually do much with vector detail. It will actually, sometimes give away the motion blur by making the detail stronger. So, to keep it nice and smooth, this is pretty much where I like to have it. So, the result is really nice.
Here, we have motion blur that is not merely unidirectional, but in fact, as you saw, as he raises his arms, their blur goes in one direction, while the center of his body continues to travel right to left. This is useful for retiming like this. It's also very useful when you're adding 3D layers, particularly Cimaware layers that really can't have motion blur applied to them. So you need to generate it right here in After Effects. Pixel Motion Blur will actually do that for you.
So Pixel Motion Blur is essential for getting this particular shot right. It provides the contrast between the skater in having it in the real world of the car, where motion is blurry, and the heighten reality we'll add next in which his amazing jump bends time.
- Advanced color correction with multiple objects and Curves
- Adding a light-wrap effect to composite into a backlit scene
- Compositing into lens distortion
- Recognizing and fixing rolling shutter
- Matching motion
- Working in HDR
- Create cinematic color contrasts with Mojo
- Customizing a film look with Looks