Saving photos from an Android ?

[elykoj]

i have an Android phone and a MacPro, when i hook up my phone to download/transfer my photos into the photo app, alot of times it will download photos that are already in the app off my phone. so not only is it transferring newer photos from phone onto the back but sometimes downloading photos that were already there previously, therefore sometimes i know have doubles or sometimes triple copies of certain photos now on my MAc.. what am i doing wrong and how can i just make setting to just download the new pictures that are not already on there???