Google+ Auto Backup: How to reject non-camera photos? Google+ Auto Backup service backs up all photos which includes downloaded pics from Web, Facebook, 500px etc. I just want it to backup my cam pics only.

How to do this? I am unable to find any option in Settings for that. Is there a directory flag or other methods to do that?

OS: Android 4.4.2 KitKat
If you have Google's Photos installed, then the following will do the same:
Bring out menu in Photos. 

Select On Device. 

Uncheck the blue cloud icon for any folder you do not wish to sync with.