For many people, myself included, switching from still to motion graphics requires us to rethink the way we prepare our files. Not only do we have the static components (composition, content, color, contrast, etc.) but we also now have a temporal component to consider and control.
When I began playing with motion graphics, I found myself consistently stumbling over the proper use of Keyframes in After Effects. Keyframes are used to mark a point of change within the timeline. Keyframes can mark the beginning of a fade in, the end of a change in size or set the beginning of a fade from black and white to color.
Though the use of keyframes is quite simple, while learning I found myself consistently forgetting to add keyframes to mark the beginning of a transition, marking only the end. This would cause the transitions specified by the keyframes to behave much differently than I anticipated. Evidently, I wasn’t alone with this problem. To help make it easier for photographers, illustrators, designers and others to begin working with motion graphics, Adobe added the Auto-Keyframe option in After Effects CS5.
Located at the top of the timeline, when enabled, the Auto-Keyframing option will automatically add a keyframe for every change you make to a layer or its attributes.
Here’s an example of Auto-Keyframe in action.
1) Create a new composition and drag your assets to the composition. Click on the Auto-Keyframe icon to activate it (Auto-Keyframe is turned off by default).
2) Drag a still image or a video clip to the composition timeline. While you position the image on the timeline, After Effects automatically adds keyframes for each of the attributes you adjust (Position, Scale, Opacity, etc.).
3) As you move through the timeline and make additional adjustments to the layer’s parameters (Position, Scale, Opacity, etc) After Effects will automatically create additional keyframes (just like it did in CS4).
Gotcha: For the most part, the Auto-keyframe feature is a welcome addition, making it easier for less-experienced motion graphics editors to begin creating in After Effects. That said, there is one potential gotcha you should be aware of, particularly when it comes to positioning items within your composition. Because the Auto-Keyframing feature adds a keyframe at the point in the timeline you make any change, it is easy to inadvertently add a number of unneeded keyframes while you set the exact position of elements, adjust type sizes etc.
For example, let’s say you drag an image onto the timeline at 0:00:00:15 and scale it to fit in the upper-left corner. A keyframe is added in both the Position and Scale fields. As you continue to work with the other elements at 0:00:01:10, you decide the image needs to be in the upper-right corner instead, so you drag it to the new position. After Effects adds a new keyframe here as well. When you play back the clip, the image will now appear in the upper-left corner, then move slowly toward the upper-right corner at 0:00:01:10. While this might be a nice effect, this wasn’t what you’d intended. Rather than a static image positioned in the upper-right corner, Auto-Keyframing has created a moving image with the addition of the first keyframe and you adjusting the position of the image later in the timeline.
The moral of the story is to use Auto-Keyframing when you have a good idea of how your composition will come together, or if you’re performing your positioning, scaling, etc. at the beginning of the timeline. If you think things might change, or you have a complex composition, you’re probably better served using the old style-keyframing by leaving the Auto-Keyframe option at its default position of off.