The Effects Library allows you to add effects to lens flare elements, dramatically changing their look and/or movement. The effects themselves may be familiar to you, since they are effects that come with Adobe After Effects. Expressions and extra slider controls were added to those effects which allow them to operate in coordination with the position and movement of the lens flare.
When you're in the Effects Library comp, you'll see 23 shape layers. These layers are actually just Reflection Shape elements, just like you would find in your Elements comp. Each one contains a different effect. The effects are in order of the ones that are most useful, with less useful effects at the bottom. To test out an effect, unhide the layer and move the Control Layer around. If you go to the bottom of the Effects Controls panel, you'll find the slider controls for the effect and you can experiment to see what they do. Most of the slider controls for each effect are evolution controls, meaning that they allow you to change the properties of the effect automatically as the lens flare moves. Note that the the slider controls come first, and the actual effect is always at the very bottom.
To apply an effect, it's just a matter of one simple cut and paste. The only thing to remember is that in After Effects, when you copy multiple items, you always want to select the top item first, then shift click the bottom item, and this will preserve their order. In the Effects Library comp, with your layer selected, go to the bottom of the Effects Controls panel, and select the effect title, the effect's slider controls, and the effect itself. Copy them, then paste them onto an element in your lens flare comp. The effect and its controls will show up at the bottom.
Since each effect does something completely different, there are a lot of possibilities in designing some cool elements for your lens flare. Also, you can use more than one effect on an element to get some really interesting results, and you could even use an expression from the Expressions Library on an effect's slider control.
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