How can I use the system information to locate 48 GB of photos?
In another forum they suggested to use a tool like OmniDiskSweeper 
(it can be downloaded here: https://www.omnigroup.com/more/) 
that can show you where the files that take up the space in your disk are.

Start by using the "File|Size Home Folder" and then explore further in the other directories if the images are not there.