SAN FRANCISCO — It’s hard to imagine how smartphones could get much better. Most are already zippy and equipped with jumbo screens, powerful cameras and face scanners.

So what else can we look forward to?

It turns out, plenty. For a peek at the future of the phone, look to Samsung, the world’s largest handset maker. On Wednesday, the South Korean company showed off a family of four new Galaxy phones that incorporate new technologies and features that may start spreading to other smartphones.

Of the four new devices, one will work on next-generation ultrafast 5G cellular networks, which means it can download a movie in seconds rather than minutes. Three of the models will have slightly larger screens and more complex camera systems than their predecessors.

And Samsung is also teasing a fifth device that can be folded and unfolded like a book to decrease or increase the phone’s screen size to suit its owner. It is expected to be available in the United States on April 26 and in Europe on May 3.