It seems to me that SVN is taking surprisingly long to upload binary files in which small changes have occurred.
I always imagined SVN would only upload the diff of a file relative to some revision when committing, instead of the entire content.
Does anyone know what the behavior is?
The behaviour is that always will be transferred only the deltas (binary or text) to the server which is calculated based on the contents of the pristine which are in your working copy. (see .svn folder). If it takes long you should check your network, cause this is often the root sources of the problem.