The iPhone 15 Pro Max Has a Tetraprism Camera—What the Heck Is That?

pcmag.com:

The competition to make the best smartphone camera is a fierce one. Apple, Google, and Samsung typically jostle amongst one another for the top spot, though you can't count out the efforts of phone makers such as Honor, OnePlus, and Oppo. In each successive generation of flagships, we see more complex camera designs that use multiple sensors and lenses to bring a wide range of creative and compelling features to the fore.

One of those features is optical zoom, or the use of lenses to increase the size of the image reaching the sensor. Smartphones have used optical zoom for years. Apple first introduced 2x optical zoom to its products with the iPhone 7 Plus back in 2016. Others have taken it much further. The Samsung Galaxy S23 Ultra, for example, offers 10x optical zoom.

This year, to stay ahead of (or maybe catch up with) its competitors, Apple has added an interesting new twist to the iPhone 15 Pro Max camera to achieve 5x optical zoom: a tetraprism. What on earth is that?

"We created a state‑of‑the‑art tetraprism design—a folded glass structure below the lens—to reflect light rays four times over," Apple explains on its site. "This allows light to travel for longer in the same space, giving you a new focal length that really goes the distance."

The tetraprism is basically a periscope, or a way to bend light multiple times through glass, which is a tool other phone makers have used in their cameras since 2017 to bring faraway subjects closer to your smartphone. For example, the Huawei P30 Pro, which went on sale in March 2019, was among the first to reach the market with a periscope camera design. The Oppo Reno 10x Zoom followed, as did the Samsung Galaxy S20 Ultra. These offered between 5x and 10x optical zoom that,