I've successfully employed the Roto Brush to cut out a foreground subject, built a grayscale precomp of the scene, and used Lens Blur to simulate a rack focus from the background of the scene to the foreground. After rotoing the foreground subject, I copied the Roto Brush effect to a pure white solid, so that it represents the utmost foreground. The effect is pretty convincing (if I do say so myself), but there's a problem...
The end of the rack focus looks great--foreground subject is nice and sharp--but the problem is that the start of the rack focus looks really fake, like the subject is in the Witness Protection Program. What I'm trying to achieve is the "bloom" that would be present around the perimeter the subject if it were out of focus optically. Instead, it's just sharply cut out, and clearly looks like it's comped over the background.
I've tried "negative choking" the roto on the white foreground solid and feathering the edges, but that really doesn't work--it just creates an in-focus outline around the subject once the rack is complete. I'm guessing what I have to do is comp the foreground subject in and blur it separately, so that the perimeter goes fuzzy. The Lens Blur is currently applied to single instance of the video clip, and is referencing a precomp of the grayscale depth map.
Any thoughts on the best way to achieve the look I'm after? Thanks!
Yes, AE's lens blur sucks, if I may say so. You would have better luck with other tools. Try the Box Blur or a third-party plug-in. Specular bloom can be simulated with a Glow preceding the blur to boost the highlights, light wrap using again blurs, mattes and the Add blending mode. Just don't overdo....
Thanks, Mylenium. Just so I'm clear: instead of using Lens Blur and depth maps, you're suggesting perhaps busting the individual "regions" of the scene into separate masked layers, and then animating Box Blur on each one individually? That's doable, if that's what you're suggesting--looks like that blooms nicely.