What permissions have I given when using certain applications?

Pics that can be seen by whom depends on your privacy settings on facebook. You can choose only you / friends / friend of friends or public. Not remembering what’s the default one.. should be friends only i guess.

I’m guessing that you made a setup choice somewhere, to send photos from the phone or camera direct to Facebook. (When I take photos they get backed up to Dropbox. I don’t have a lot of faith in Facebook’s privacy settings.)

To my knowledge, nothing on my phone goes to FB unless I post it manually.

What about Instagram? Do you have that app on your phone? That could also be a conduit, I think (though I wouldn’t know for certain, as I don’t use it, but I see a lot of my friends’ photos get to FB that way.)

I probably didn’t explain this well enough. Fb has only basic iOS permission to access my photo library. In my mind I intend that permission to mean when I go to upload a picture they will be allowed to open the folder through the app.

Think of it this way: Have you ever granted your email provider a special permission regarding your photo library in order to upload a picture attachment to an email? No!

So, what is this permission allowing precisely? The right to peruse my photo library?

From a quick Google search, it sounds like you have Photo Synching switched on in Facebook. I agree that such a feature should not be the default (if, in fact, it was for you). Here are the instructions from Facebook Help Centre for changing that setting:

Open the Facebook app and tap
Scroll down and select Account > App Settings > Sync Photos
Choose Don’t sync my photos

From your iPhone:

Open the Facebook app and go to your profile
Tap Photos > Synced
Tap the gear icon in the top right
Tap to turn Photo Syncing off

thanks