If you owned an an early generation iPhone (or any camera phone or digital camera) before it was equipped with GPS, chances are you have photos in your camera roll that have no location information. iPhones now geotag your photos automatically (unless you have turned the feature off), which helps with categorizing them and allows them to import into your "Places" album. You can, however, add locations to your "dumb" photos using Apple's Photos app on a Mac. Here's how to do it:
iOS 11 adds a tool that, in theory, ensures your camera is perfectly perpendicular to a horizontal surface you are photographing (so, say an object on a table top or on the ground). The feature is integrated with the grid tool, so it will help you take squared off, symmetrical photos. To use it, go to Settings -> Camera and turn on the grid. Now when you point your camera toward the ground, a pair of crosshairs will appear, one fixed and one floating. Line them up to ensure your photo is level.
Digital photos contain lots of metadata including information about the camera they were taken with, a timestamp and, if the camera is equipped with it, GPS data. This data can be viewed by anybody, so it raises privacy concerns. While there are many apps that allow you to edit this data, you can also simply turn off location services for your iPhone's camera in Settings -> Privacy -> Location Services -> Camera. Check off "Never."
While lens filters for the iPhone's Camera app have been around for several iOS generations now, iOS 11 not only changes the available filters, but changes the user interface as well. Apple touts them in its iOS 11 preview:
"New professional-quality filters take the camera on iPhone to another level. Portrait photos are more expressive. Skin tones more natural. There are even filters for applying classic looks to your portraiture photography."
The QR code reader should be on by default if you have iOS 11 installed. Simply focus on a QR code and your iPhone will notify you that you can go to the website on Safari, or whatever other action the QR code offers (join a Wi-Fi, email somebody, etc.). If for some reason it isn't on, head to Settings -> Camera and toggle on "Scan QR Codes."