trouble viewing iphone photo backups

Ive never really understood where the iphone is backing up my photos, though i do have the sync photos button checked when backing up.

I simply do a manual drag and drop of all my iphone photos (when my phone is connected) into aperture so that i can actually access them.. I store them in a folder called iphone.

However I am assuming that since i have sync photos checked itunes is backing up my photos also.. but i cant tell to where?? How do i figure this out.. and perhaps stop using aperture & doubling up when i maybe dont need to...

my laptop runs 10.10.5 yosemite & im using an iphone 8.

thanks