The Echo Effect

The Echo effect creates copies (echoes) of a layer by adding duplicates from different places in time.

In the Echo.aep project you’ll find in the Chapter 18 folder of the exercise files. In Figure 18.1, we see the original video clip without the Echo effect applied. This clip shows my friend, Paavo—a video editor at lynda.com—doing some of his sweet unicycle tricks.

Apply the Echo effect to the stair jump PRECOMP layer in the stair jump composition. The default results in this case don’t look all that great. To get a better idea of what Echo is doing, change the Echo Time (seconds) value to – 0.35, and change the Echo Operator value from Add to Minimum. Also, take the Number of Echoes to 8. Then you’ll see what’s really going on here.

The Echo effect creates echoes in time by blending frames from different times together into one composite. This creates a visual “echo” as the frames ripple into one another. Echo works well for those times when you want to really exaggerate an action in video, and slow motion just doesn’t pack a big enough punch. It also can create visually interesting motion graphics because the echo effect creates a trail. In this example, Paavo’s stair jump was in a beautiful and natural arc, which looks awesome when echoed.

The Echo Time (seconds) parameter determines where, in time, that the echoes come from. A negative value will create the echoes from the past, and a positive value will take create echoes from the future. Remember that this value is the time between echoes in seconds, not frames. Figure 18.3 shows the Echo Time value at –0.15, which is much shorter than what we saw in Figure 18.2. Notice how the echoes are now much closer together.

In Figure 18.4, I’ve adjusted the Echo Time value to a positive number. Both Figures 18.3 and 18.4 show the exact same frame. Thus we see how negative values take previous frames to make echoes, which causes the current frame to be the beginning of the trail. A positive value causes echoes to be from upcoming frames, which causes the current frame to be the caboose in a choo-choo train of echoes.

The Number of Echoes parameter is self-explanatory, as it controls the number of duplicates it creates. Note that if you’re not seeing all echoes created by this value, it’s probably because your Echo Time value is too far away from 0, which indicates that your echoes haven’t started yet, or they’ve already gone off screen.

The Starting Intensity and Decay properties are very similar, and they’re also connected. The Starting Intensity value controls the opacity of the current frame. Easy enough. The Decay value controls the opacity of the echoes. However, it is based on the Starting Intensity value, and then each echo decays more, based on the Decay value. For example, if your Starting Intensity is 1, that is the equivalent of 100% opacity, or completely opaque. If you take the Decay to 0.5, this is the equivalent of an opacity value of 50%. The first echo would be at 50% opacity, the second echo would be at 25% opacity (50% of the second echo), and the third would be half of that. If the Starting Intensity value were 0.5 and the Decay value were set at 0.7, the first copy would be 70% of 50%. The next copy would be 70% of that, and so on. As you can see, there’s a lot of control here.

Finally, the Echo Operator property controls how the echoes blend together. Remember that we’re dealing with transparency here, so if we want to combine multiple frames—at least with this video—then we’ll need to use a blend mode of some type. And that’s what the Echo Operator allows us to do. Most of the modes, such as Add, Screen, and Maximum will return a much lighter result. These are great for creating ghost-like effects, or other soft, ethereal or angelic effects. We’ve been using Minimum as it returns a dark result, which works well with this footage that has a lot of blown out highlights.

The Posterize Time Effect

The Posterize Time effect is as simple as it gets. The purpose of the effect is to conform a video layer to a specific frame rate. The only parameter for this effect is Frame Rate, which is the absolute frame rate. This effect is useful for conforming video to a film frame rate (24fps, which is also the default value for this property).

You can also achieve this same result with a little more effort by precomposing a video layer, and in the Composition Settings dialog box, change its frame rate in the Basic tab, and the click the Advanced tab and select the option with one of the longest names of all time: Preserve frame rate when nested or in render queue. This will allow the contents of the precomp to play at any frame rate, regardless of the frame rate of the parent composition.

I honestly haven’t found much use for this effect. While I do use mixed frame rates, I’m typically combining higher frame rate footage into my 24p comps in order to get slow motion. But Posterize Time doesn’t do that. Using the Posterize Time effect to conform 60 frame per second footage to 24 frames per second basically does the same thing that After Effects already does when you put 60fps per second into a 24fps composition.

Although, I will say that if you ever wanted to simulate one of the most popular video effects from the 1990s, take the Frame Rate value of the Posterize Time effect to around 8.

The Time Difference Effect

If you’re familiar with the Difference blend mode, you know that one of the uses of it is to be able to compare the pixels of two layers to see where they differ. Hence the name. The Time Difference effect does the same thing, but it allows you to compare frames from different places in time on the same layer. Now, before you go skipping on ahead to Time Displacement, let me tell you that this effect has some pretty useful features, especially for color correction and visual effects workflows.

To start out, let’s open the Time Difference.aep project from the Chapter 18 folder, and apply the Time Difference effect to the Chad with Hand Dot layer. This is just a video clip of me being a goon in front of a green screen. So, when you first apply this effect and the screen goes gray, my sense of embarrassment subsides.

The reason the screen goes gray is because blending things in the Difference blend mode is meant to compare things. When two identical objects are compared, the result is a solid color. With Difference the layer blend mode, identical layers become black. With the Time Difference effect, identical frames become gray. And by default, the Time Difference effect compares the current frame with the current frame.

Before we go any farther, let’s actually adjust this effect so that we can see something more than just gray here. Change the Time Offset (sec) value to 0.2. You will then visually see where these frames are different, because the difference (the non-identical pixels) will not be gray.

As has been our tendency throughout this book, let’s look at the properties in this effect from the top down. The first parameter is Target. This drop down controls which layer is being compared to the current layer. It defaults to the layer the effect was applied to, but it can be any layer, and the layer doesn’t even have to be visible to be used as a Target.

The Time Offset value is the amount, in seconds, that the Target layer is offset from the current time. To compare the same frame, keep this at zero. Contrast increases the intensity of the difference.

The Alpha Channel value is very interesting. It allows you to change the Alpha Channel of the result, which opens up a lot of doors. Here’s the gist of what each option does:

• Original—No change to the alpha.
• Target—Uses the alpha channel of the layer chosen with the Target property.
• Blend—blends the alpha channels of both the target layer, and the layer the effect is applied to.
• Max—Uses whichever alpha channel is more opaque between the target layer and the effect layer.
• Full On—Forces the alpha channel to be completely opaque.
• Lightness of Result—This is where it starts getting interesting. Lightness of Result will create a new alpha channel that is based on the difference result only. This option creates an alpha based on the lightness of the result.
• Max of Result—This is similar to Lightness of Result, but the result is usually brighter.
• Alpha Difference—Uses the difference between the alphas of the target layer and the effect layer.
• Alpha Difference Only—This returns the same alpha channel as Alpha Difference, except that the entire RGB result becomes white.

So what can you do with this wackiness? One of the great purposes of this effect is to compare color adjusted frames and instantly see their differences.

Another great purpose is to use the end result for visual effects. Let’s use this example, and say I wanted to create some fire around my hands a la that guy in Fantastic Four. I could roto-scope my hands as they move around. But it would be much easier to simply use Time Difference to create a layer with an alpha channel that was roughly my moving hands, as in Figure 18.7.

In this example, I set Time Offset to a small 0.07, enabled Absolute Difference, and took the Alpha Channel result to Max of Result. There’s some extra pixels around the edge of me, but we could easily mask that out. The point is that we’ve isolated the hands for the most part, with a modicum of effort. We can then add an effect like Particle Playground and use the Layer Exploder to create the illusion that my hands are on fire. What else can be done with Time Difference? The potential is pretty big with this one.

The Time Displacement Effect

As we saw back in Chapter 7 when we looked at the Displacement Map effect, you can use the lightness values in an image as a controller to shift pixels. Similarly, we can use the lightness values in a map as a controller with the Time Displacement effect, only the map will not shift pixels spatially. The map will shift pixels in time.

To see some hot displacement action, open up Time Displacement.aep from the Chapter 18 folder. Apply the Time Displacement effect to the stairsdock PRECOMP layer in the stairsdock composition. As with almost any displacement effect, when you first apply it, it attempts to use itself as a displacement map, and it looks terrible.

If you solo the grayscales.tga layer, you’ll see a grayscale map I’ve created to control this effect.

Change the Time Displacement Layer value to the grayscales .tga layer. You’ll then see that the white area of the displacement map shifts the footage pixels forward in time, the gray area has no effect, and the black area shifts the pixels back in time.

The only parameter we really need to be concerned with here is Max Displacement Time [sec] which controls the maximum amount of time from which pixels will be taken. At the default value of 1, white pixels in the controller will shift those areas of the footage ahead 1 second. Black areas in the controller will shift those areas back 1 second. Other values will adjust in between those values.

To see another example, solo the fractal noise PRECOMP layer.

Next change the Time Displacement Layer value on the stairsdock PRECOMP layer to the fractal noise PRECOMP layer. Figure 18.11 shows the result (showing a frame that is more illustrative of what is happening).

The Timewarp Effect

The Timewarp effect is one of the more powerful effects in After Effects. We can use it to slow down and speed up time, and we also have control over the speed/quality of how that is done. As we’ll see, the Timewarp effect can also add motion blur to footage that is already rendered. It also has features similar to the time controls in the Stretch column of the Timeline panel, except that the Timewarp effect allows us to also animate speed changes. For practice with this effect, you can open the Timewarp.aep project from the Chapter 18 folder.

Many of the settings in this effect (such as motion blur, time stretching, and frame blending) can also be seen in different forms in the Timeline panel, although the Timeline and the Timewarp effect act independently of each other.

First we need to talk about the Method drop down, because this is one of the greatest aspects of this effect. When footage is slowed down, it creates a serious dilemma. Let’s say you have a piece of footage that is 30 fps. If you slow it down to 50% of its original speed, then it will be twice as long. Because it is twice as long, After Effects will have to do something for all those extra frames. Think of this like typing in a Word document. If I type:

and then I decide to stretch those fives across the width of the document, I’ll have to do something to fill in the gaps. I can duplicate the numbers:

The point is, that something has to fill the gaps between them. Frames in time work the same way.

The Method drop down is key because it determines how After Effects will stretch the footage. Whole Frames renders the fastest, but also the lowest on the quality totem pole. Whole Frames just duplicates frames to fill the gaps. If you slow down your footage a great deal, the footage will seem to stutter during playback. The Frame Mix option is essentially a cross dissolve transition from frame to frame. The “real” frame will fade out over time until the next “real” frame completes the process of fading in. If you have something with linear motion, such as a race car going from one side of the screen to the other, this could do the trick. It takes longer to render than Whole Frames, but also looks better (usually).

The other Method deserves its own paragraph. The Pixel Motion method is nothing short of digital magic. Pixel Motion attempts to create vectors or paths that connect pixels in one frame to pixels in the next frame. In effect, it attempts to recreate brand new frames. This is very helpful when you need details and a cross fade, like that in Frame Mix, won’t help. Say for example, you have some footage of a fight scene. Pixel Motion can help you get the most detail out of the slow mo shot. And in most instances, it works remarkably well. Also, you’ll notice that once Pixel Motion is selected, several other properties of the Timewarp effect become selectable.

Let’s see the digital magic of Pixel Motion in action. For this example, we’ll use a crystal clear video clip from Artbeats.com. Import the file CJ121.mov from the Artbeats folder in the Media folder of the exercise files. Make a new composition with this footage and apply the Timewarp effect to it. I’m going to leave the Speed value at the default 50, which will play this clip back at 50% of the speed of the original clip. Figure 18.12 shows two adjacent frames of the video in Whole Frames mode, so After Effects has not changed the original content. When the video footage is slowed down, the small difference between these two frames will seem like a much larger jump.

Just by way of comparison, let’s see what these frames look like when blended using Frame Mix. You can see hard edges and other visual stutter effects caused by Frame Mix’s cross dissolve-type blending.

Next, we’ll change the Method value to Pixel Motion. This causes After Effects to create an intermediate frame in between these two frames. Figure 18.13 shows the frame that After Effects created to transition between these two frames. Not bad!

The Speed property controls the speed of the clip. I’m not sure I understand why there isn’t a % sign here, because that’s exactly what this value indicates. If Speed is set to 100%, then the clip will play back at regular speed. If the Speed value is higher, the clip will play faster, and if it is less than 100, it will slow the clip down. The ability to animate this property adds a lot of power to this effect. For example, if you had footage of an athlete doing a long jump, you could play the footage at regular speed until the athlete started their jump. At that point, you could animate the Speed value to slow the motion to accentuate the jump.

One of the problems that you’ll run into with Timewarp is layer duration. For instance, if you had a two-second clip that you wanted to play at half speed, you would expect that clip to then play for four seconds. Unfortunately, that’s not the case. Timewarp would actually play the first two seconds of your clip at half speed, and then when the duration of the source layer ended, it would stop playback (so you’d only get the first half of your clip). What can you do?

Well, the solution to this problem is to precompose the layer in a precomp that is as long as you need. In this hypothetical example, you would create a precomp that is four seconds long (consisting of your original two seconds of footage, and then two extra blank seconds). Apply the Timewarp effect to the precomp in the parent comp, slow it down to half speed, and enjoy the heck out of that magic.

Also note that Timewarp really likes being the center of attention, and doesn’t like sharing the spotlight. If you have other effects applied to your layer, regardless of what the effects do (from blurring to keying) or what order they are placed in, the Timewarp effect will often turn off those other effects. The solution here, as before, is to precompose the layer with the desired effects, and then apply Timewarp to the precomposed layer in the parent comp.

The Motion Blur property is another one of the very impressive items on the resumé of the Timewarp effect. We know that After Effects can add motion blur to layers that you animate. This simulates the blur that is created by quickly moving objects when filmed with a real camera.

But what happens when you get some footage that is already rendered, such as a render from a 3D application or a clip of stock video footage, and the motion in the video doesn’t match the motion blur of the rest of the composition? By selecting Enable Motion Blur in the Timewarp effect, After Effects will look at the footage, and by using the same system of vectors it used to create the intermediate Pixel Motion frames, it will analyze the motion in the video, and add motion blur. You can even adjust the Shutter Angle property to control how much blur is added! For someone who works often with 3D artists, I can tell you that this is a lifesaver when you need it. Because of how much computer brain sweat goes into analyzing already rendered footage to apply motion blur to it, this property will slow down your render time considerably. But for those times when you have a video that wasn’t rendered with enough blur for your liking, this parameter is worth the wait.