Surely there must be some technical way that isn't usually advertised as the data of the image is there in the thumbnail?
no - you can not create a high resolution image from a low resolution image - do not even understand why you would expect there to be one
How was the backup made? What are the sizes of the photo files on the backup?
It was over a year ago but I believe I just dragged and dropped iPhoto Library, or I copied and pasted. I don't have the MBP that these photos were on anymore, I sold it to a friend and reformatted the HD.
Could there possibly be a way of retrieving them from the MBP even though the software has been overwritten?
I don't know how big the photo files were but I would imagine somewhere between 1-4MB per photo.
I guess I do not follow
it appears the back up is only thumbnails.
And I ask what is the size of the photos on the backup that you stated you have
As potential solutions
again I said
Software like File Salvagehttp://subrosasoft.com/software/filesalvage can find and restore files if they have not been overwritten - the free download will tell you what can be recovered - you have to purchase to actually recover the photos
That is a potential solution -- if the photos have been overwritten then there is no solution - the onluy way to tell is to down load the softrware and run it on the MBP to see what can be recovered - as I said