Question on Ferris Bueller's Day Off ......?

Cameron is focussed so intently on the painting while, at the same time, is intently focussed internally as well. The constant shift between the two images, and the tightening of the image onto the single portion of the painting, is reflective of this. It leads into Cameron's change towards the end of the film, in which he has decided to face his father and change his life. This event, in the museum, allows the audiance some more understanding of just how much Cameron is internalized and how he has focussed so much energy into a single aspect of his life, that being his need to please his father.