Flash Drive storage question

I recently purchased a shiny new 128 gb storage sd card for my macbook air with the hopes of moving my iPhoto library to that drive.

My iPhoto library is about 77 GB (this is what shows in every scan and also what shows as copied when I copy it over) but when I copy it over to the sd card it takes up about 110 GB worth of drive space. I have made sure that there is nothing in the trash can in iPhoto or on the computer but it still takes up that extra space. Does anyone have any idea why this is behaving like that and if there is any way to fix it.

Would it help if i exported my iPhoto library from inside iPhoto out to the sd card and then chose that as my library the next time I opened iPhoto?

Any help is appreciated.

Normally SD cards come pre formatted from the factory as Fat-32. That particular format is sloppy and will result in what is called cluster slack. The solution is to reformat the SD card to the Mac format. (HFS+ Journaled) Reformat the SD card using Disk Utility and then try again to copy the 77 GB of photos.