Partitioning a large directory into subdirectories by size

Since I’m not fond of carrying around all my photos on a cell phone where they’re perpetually at list of loss, I peridiocally dump the image and video files to a drive on my desktop for later burning to optical disc.1 Saving these images in archival form is a hedge against the bet that my existing backup system won’t fail someday. I’m using Blue-Ray optical discs to archive these image and video files; and each stores 25 GB of data.