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Express Your FlareWorking with Light Factory and expressions in Adobe After Effects
There are varying methods of applying lens flares. The common denominator is the implementation of an alternate layer to to carry the flare effect. Another common part of the composition equation is the use of a layer with an alpha channel to control where the light source breaks through the obscuring element, causing a flare.
The basic principle of the lens flare requires a light source (reflections included) to point directly into the lens. As with Knoll Light Factory, most plugins honor the first code of lens flare. Knoll LF also allows the user to disregard physics and create all kinds of irregular designs.
After Effects comp setup
Although the alpha channel you want to use as an obscuration layer does not need to be visible or embedded in the same layer as your comp image, it does need to reside in the composition. I've imported a piece of 3D text with an alpha channel and a background image.
The third layer is a Black solid to which I'll add my Knoll LF components. While I generally start with the "Light Factory" subset and change the options to create my own custom light, there is enough in that one subset alone to merit a separate tutorial (which you can download in PDF format here).
While they are incredibly customizable and quite enough for most scenes, one of the reasons for staying away from the all encompassing subsets ("Light Factory," "Light Factory Spectacular," and "Light Factory EZ") is the lack of keyframe control over the components of the flare separately.
I'll add four different elements of a lens flare. LF Chroma Hoop, LF Poly Spread, LF Star Caustic and LF Spikeball. By default it looks like a pretty average flare.
As an After Effects user, you know that you could apply one of several different transfer modes to the layer in order to composite the flare over the rest of the scene. However, the transfer modes also impart their own effect to the layer against layers below. Knoll has provided "Unmult." It seems a rather inert plugin, until you use it with something like a black background lens flare, when it pulls the blacks right out. Screen transfer mode works quite well most of the time.
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