Join Rob Garrott for an in-depth discussion in this video 031 Creating motion blur in After Effects, part of Design in Motion.
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Hi! Rob Garrott here! Welcome to Design in Motion, the weekly series where we explore important fundamentals in the world of motion graphics. In this edition we're going to take a look at motion blur in After Effects and how it can be used to make your compositions more interesting and realistic. Let's get started. Now motion blur is an artifact that was first experienced in motion picture cameras that used film footage. A motion picture camera has something called a shutter in it that it used to control how much light gets to the film back of the camera. While that shutter is open, if an objects moves within the frame, then that object is blurred.
Everything that's not moving in the frame remains crisp. That artifact is called motion blur. It's a characteristic of video cameras and film recorders and it is something that we've all grown accustomed to seeing. Computer animation software, like After Effects or Cinema 4D, do not actually produce that artifact naturally. The programmers of them had to put it in there for us. That's actually a good thing, because it allows us to control how much motion blur we have, or if we have motion blur at all. There are times where you don't want to have it.
In After Effects, a motion blur is kind of a two-step process. Now I have a very simple composition here and this is a simple shape layer of a square moving across the screen from left to right. I'm going to do a RAM Preview by hitting 0 on the numeric keypad. As you can see, the square is moving from left to right across the frame just fine, but as it moves, there's a crispness to the motion that just screams computer-generated. In reality, all of us know that this was generated in a computer, but we still want it to feel very natural and realistic, and that's where motion blur comes in.
Now I've got another composition here. It's the exact same comp with a square moving across from left to right. What I'm going to do in this composition though is I'm going to activate motion blur. Now activating motion blur in After Effects is a two-step process. Now step one is to click on the layer that you want to activate motion blur for. You don't actually have to click on the layer; it's just something I like to do, because it allows me to trace visually across the screen to the Switches Column, where you're going to actually commit step one. Step one is to activate the motion blur switch for that layer.
And you'll notice when I click on that button, you'll see that the word motion blur appears. That's to remind me that I've turned on motion blur. That is not enough. If I were to do a RAM Preview right now, I wouldn't see anything happening. So in order to see the motion blur visible on the comp, I have to tell After Effects that I want to actually preview that motion blur. And I do that by turning on this switch right here and you'll see that the little pop up says Enables Motion Blur for all layers. So I'll click on that and now I can do another RAM Preview and I'll hit 0 on the numeric keypad.
And as my object moves across screen, it's doing the exact same motion, but there's now a very smooth blur happening from frame to frame. I'm going to stop playback and just park on this. Now because I've got it selected here, you can see the wireframe for the layer, I'll deselect that by clicking in the gray area. And now you could see if there's a very slight blur. That blur is the interpolation of After Effects calculating how far the pixels have moved from frame to frame, simulating that motion blur effect. Now you can control this motion blur in the composition settings.
Now I'll hit Command+K or Ctrl+K on the keyboard and in the Advanced tab are the Motion Blur settings, and there are four settings here; Shutter Angle and Shutter Phase, they determine the intensity of the Motion Blur effect, and then Samples Per Frame and Adaptive Sample Limit determine the quality of it. Now the Shutter Angle is the most important one here. This tops out at 720 degrees, but you can use this to increase or decrease the amount of motion blur. I'm going to max this out at 720 degrees by just clicking and dragging all the way at the right.
You can see here that in the Preview window, the motion blur has gotten much more intense. I'll hit OK here and then do another RAM Preview by hitting 0 on the numeric keypad. And as you see, the object moves through the frame with much more blur. Let's park on it. You can see that there's a bunch of steps here in that, and that's controlled by the quality. And if I hit Command+K again to get back to the Composition Settings and go back to the Advanced tab, I can dial down the Samples Per Frame. The Samples Per Frame and Adaptive Sample Limit work together to control the quality of the motion blur.
I'm going to take my Adaptive Sample Limit and scrub it all the way down to 16 and hit OK, and you notice that nothing happened. That's because if I go back to the settings here, you'll see that the Samples Per Frame is still set at 16. If I dial those down to the lower limit of 2, now I start to see a very steppy motion blur. And there actually may be a stylistic reason that you'd want to do it. In practice over the years, I haven't ever really messed with these values, but it's there if you need it. I'm going to turn that back up to the default of 16 and 128; 16 for the Samples Per Frame and 128 for the Adaptive Sample Limit and leave my Shutter Angle at 720, and you could see I'm now back to that nice smooth blur.
Now the next thing I want to talk about is the idea that not all layers in the composition need to have this motion blur. There are times where you may want to make a point by having one object have motion blur and another object not have motion blur. In this next type example, I've got some layers here and I'll do a RAM Preview. So as you can see, I have two simple sentences here, motion blur good; no motion blur bad. Now there may be a time, like I said earlier, that you'd want to have one set of layers not have motion blur. And that's the beauty of After Effects, is that it's completely optional on a layer-by-layer basis.
I'm going to turn on motion blur for the Good layers and that's layers 3 and 4 here, and I'll activate that motion blur by doing that. You can see that it immediately killed my RAM Preview for the comp. And if I back up in time, I still don't see the motion blur. That's because remember, I have to activate it here, when I turn it on. I can now scrub through and see a very nice smooth motion blur for that. If I do a RAM Preview, I've got motion blur good, no motion blur bad.
Let's go ahead and crank up that motion blur so that we get a really strong effect. I'm going to hit Command+K or Ctrl+K on the keyboard to bring up the Composition Settings and go the Advanced tab and I'll crank that Shutter Angle up to 720, which is the max. And you can see I have a much more intense Motion Blur effect, and let's do another RAM Preview. So as you can see in this example, the motion blur good layers have a smoothness to their animation that really just isn't present in the no motion blur layers.
As you can see, motion blur has a huge impact on the look and feel of your animations. I have a couple of clients that don't like it, but generally speaking, I always have it on. For more great After Effects courses, be sure to check out the After Effects section on lynda.com. That's it for this edition of Design in Motion. Keep it moving and I'll see you next time.
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