Ok, lets take a moment to talk about my current favorite After Effects filter. It’s something that I haven’t used much in the past, but on my last project, I ended up applying it to several layers in each composition. As an example, I’ll use this simple background.
I created these graphic elements to set behind text. They look interesting, kind of like a DNA chart, and they animate well, with individual pieces sliding around and dissolving over each other. Graphically speaking, it fits the technical nature of the project, but it’s too sharp and distracting as it is. I could blur it evenly, but that would just look like shapeless blobs moving back and forth. Time for something a little more subtle.
Compound Blur applies diffusion to an image based on the grayscale values of another image. To control it, I made a simple linear gradient that whited out most of the area where I planned to put text. I then added the Compound Blur filter to my moving blocks, and set my gradient as the blur layer. After tweaking the blur amount and lowering the layer’s opacity, we have what we’re looking for (with some images, heavy Compound Blurring can create blocky artifacts, but these can be blurred again by a masked adjustment layer).
The areas where the gradient is lightest, the blocks are the most blurred, and the upper left corner of the image, sharp detail is still visible. This is simplest use of the filter; just a still linear gradient controlling the blur amounts. However, animated gradients or moving footage can create interesting effects, and if you can make a pseudo-depth map for video footage, it’s a good way to add or enhance depth of field blurring, even though the Lens Blur may be a more precise option.