Well, the selective focusing technique is first year cinematography. It's also something our eyes do all the time. When we see it in films we sort of induce the effect, our brain precedes the mouvement of the lens, that's why it's an effective technique. Our brain is used to the focusing mouvement of the eye. And it's probably the mouvement that triggers the brain's understanding of what's to come. In a still image the mouvement is not there, the brain needs to explain and interpret the effects of depth. If you put the secondary character out of focus, then everything at that depth and within the limits of the focal length (this would have to be done in post work) would have to fall within that logic. ie: gradually become out of focus. Not easy to do. Cheers, Blue

Un coup de dés jamais n'abolira le hazard
S Mallarmé