Are uploaded photos shared

A Google+ album can have just one sharing setting at a time.

• But you can choose and share only selected photos from that album, then the recipient can see only those images, not the whole album - as Google+ creates a new album for those shared photos. The rest stays private.

You can also move / copy those selected photos to a new album with wider sharing settings.

Note: If you tag someone in a photo inside an album, they see all the photos in that album.

Read more from Google+ Photos support: https://support.google.com/plus/answer/1407859?hl=en&ref_topic=1257351

An article about Google+ photos, albums and how to organize them: http://googleplushelper.blogspot.fi/2013/06/google-and-your-photos.html

For private posts, that is correct, and an intentional decision. There is no BCC equivalent in Google+ except to create separate posts. This is intentional because the people commenting on the post may expose each other while posting comments.