Wow, how difficult could it be? Very difficult!
I posted a photo shoot of some bands to a Facebook 'group' for the record company. Now, it seems unlike every other kind of post, photo or photo album in Facebook, ones in groups, even public groups, cannot be shared. Next to the 'like' and 'comment' links there is no 'share' link at all. Looked around for all kinds of other ways and nothing.
One of the bands then asked me to post the photos to their 'page' - note that this is a 'page' not a 'group' (although I don't really know why Facebook has these two separate concepts). So although I didn't really want two copies of the photos on Facebook, I uploaded them again to an album on my own personal page. Titled and re-tagged them all and thought I was almost done...
So, I clicked on one of the photos of this band, yes, I get a 'share' link, phew. The share dialog box comes up, defaulting to 'On your own timeline', I click on that to drop down the other options.. and what do you get? Two more choices, 'On a friend's timeline' and 'In a group'. But wait, what about sharing to a 'page', nope, you cannot do that!
This isn't about permissions, you can post a photo to the page if I upload a new copy, but you can't share an existing photo to the page.
I wish Facebook would sort out this stuff.