With iOS 9.2, Apple has enabled iPhone support for the USB Camera Adapter for getting your photos on your iPhone’s camera roll. When you plug the adapter into your iPhone and camera, your iPhone will automatically open the Photos app and allow you to import photos or videos.
Per Apple, “After you connect the Lightning to USB Camera Adapter, your iPad [and now, iPhone] automatically opens the Photos app, which lets you choose which photos and videos to import, then organizes them into albums.”
Compatible models include the iPhone 5 and newer. It also works with the iPad models that have a Lightning port.
[Updated: An earlier version of this article referenced that the Lightning to SD Card Camera Reader support was added in iOS 9.2. However, support for the SD Card Camera Reader was previously available on the iPhone.]