2 Replies Latest reply on Mar 29, 2011 7:17 AM by Colin Brougham

    Faking rack focus: how to blur a rotoscoped foreground element

    Colin Brougham Level 6

      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...

       

      START:

      rack-focus-start.png

      END:

      rack-focus-end.png

      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!