Newer iPhones without the Home button have a handy camera icon, but there's a quick shortcut that works on all iPhones

Just swipe left on the lock screen and you'll launch straight into the camera app, so you won't miss the shot

Only the photos you just took are accessible in this mode, so you don't need to worry about people snooping

To access your full photo library, you still need to authenticate with Touch ID or your passcode

Swipe left also works on newer iPhones, so you can use it for fast camera access there too