I think the sending phone is smart enough to turn on its own Bluetooth transceiver, but it is not clear if the receiving phone will do so. I did read that pairing is automatic so the devices do not need to have been previously paired.
In Android 4.1 Jelly Bean, Android Beam -- that's the NFC-based device-to-device transfer service -- has been augmented to support sending photo and video content. This is done from within the Gallery app, and can be activated by holding two NFC (Near-Field Communication)-supporting Jelly Bean devices back-to-back while one has an image or video open. Then, when prompted, tap the screen to send, just like earlier Android Beam incarnations. File transfers themselves are handled by Bluetooth, so depending on your device's Bluetooth version support, your transfer speeds may vary.