I am new at using the rotobrush tool. The mechanics of it I understand...it's great. I have roto'd out my actor and now I want to simulate some depth of field in the shot. How would I do it? I am looking at keeping the actor in focus for the shot and gradually bring the background from a blur to completely in focus with the actor. Another thing I would like to do is to start the shot with the actor in focus and the background blurred and then switch it so that the actor is blurred and the background is in focus.
Thanks for everyone's time!
This isn't a Roto Brush-specific question. This is a basic question about compositing. So, keep in mind that you can use what I say here for any rotoscoping, keying, or other techniques for creating transparency. (Also, you can use what you learn from these areas and apply it to Roto Brush work.)
One way to apply an effect to just one area of an image is to duplicate the layer, create transparency on the top instance of the layer (with Roto Brush, rotoscoping with masks, using keying effects, or whatever), and then apply the blur effect (or whatever) to only one of the two instances of the layer.
Another way is to duplicate the layer (sensing a trend yet?) and use the instance with the Roto Brush effect as a track matte for an adjustment layer. Then apply the blur effect (or whatever) to the adjustment layer.
Compositing is complex. It's not a one-click/one-layer/one-effect job. You will often use many duplicates of layers with many different effects to get things just right. If you follow the links that I provide throughout this message, you'll find that the pages that I link to contain lots of information and links to in-depth articles and tutorials. For example, the Mark Christiansen tutorial that I point to in this post demonstrates the first method that I described.