What is a periscope camera (and why it’s nice to see one on the iPhone 15 Pro Max)

While the iPhone 15 Pro gets a potent 3x telephoto camera at a focal length of 77 mm, the iPhone 15 Pro Max goes much further to a 5x optical zoom at 120 mm. Think of it like that: a "5x" optical zoom gives you 5 times the optical magnification as compared to your main camera. So, 120 mm is great for close-ups, for catching wild animals or sports from distance: it offers many creative opportunities to be explored by the artist in you.

Apple calls the periscope design in the iPhone 15 Pro Max "an innovative tetraprism design" and adds that there's also a combined optical image stabilization and autofocus 3D sensor-shift module, Apple’s most advanced stabilization system yet. The tetraprism catches the light from the lens, reflects it four times through the glass structure and by making it travel for longer, it in fact creates the needed separation between the lens and the sensor for the zoom magic to happen. If all of this sounds complicated, don't be afraid, just keep on reading and we'll explain it in the simplest of terms.

Before we go any further, one last dip in the dry technical specs. The new 120 mm periscope lens features a 25% larger sensor (compared to the sensor found in the iPhone 14 Pro Max), 100% focus pixels and a bright f/2.8 aperture. More than most of the photographers out there will appreciate this 120 mm, f/2.8 lens for sure, as this is a serious portrait standard. Enough specs, already!

The origins of a periscope as an optical invention can be traced to several centuries back. Up until recently, most of us thought of it as ‘that tube to see through’ on a submarine. Things are different these days, and phone users often encounter the term ‘periscope camera’ in headlines, or even own phones with such cameras.

In the simplest of terms, think of it as a special lens system that gives you extra optical zoom capabilities. Typically, optical zoom is achieved by moving a lens element further from the image sensor – the more you want to zoom in, the further that element has to go. But of course, nobody wants a phone with a huge lens module sticking out. A periscope system solves this using a non-standard design and lens alignment: sideways. Thus it gives you ‘real’ optical zoom instead of digital zoom. The difference is huge, but let’s talk it over again.

Digital vs. optical zoom

Before the introduction of secondary (and tertiary, or more) camera setups, there was only one camera on the back of a standard phone. It was sort of a swiss-army knife tool: it was used for indoor, outdoor shots, portraits, snapshots, literally everything. Every now and then, though, users had to take a photo of something that’s either distant or small. That’s when one learns about the digital zoom pain: as you enlarge your image from the single-camera setup, quality degrades and artifacts bloom. That, in a nutshell, is digital zoom. You take a picture, clip out the surroundings of your subject, and enlarge what’s left of the image. Cropping out of a picture with a higher megapixel count produces better results, but still, it’s nowhere near as good as optical zoom.

Optical zoom is quite different. Yes, no doubt it too leads to deteriorating picture quality, but it’s far subtle and overall incomparable with digital zoom. Like the name suggests, optical zoom is possible because of optical alterations in the lens itself. Again, for the magic to happen, there are physical limitations and prerequisites: the front element of the lens has to be positioned further away from the sensor (the sensor is where your scene is captured and turned from light to zeros and ones, which is turned by the device as a beautiful image on your screen).

The best example of a gadget with optical zoom capabilities is your mom’s point and shoot camera. Remember the lens on that compact thing used to protrude? Now, with some extreme exceptions (we’ll list them below), phone manufacturers are not fascinated with the idea of producing a device with a 4 inch tube, sticking out of the back that has to extend and retrieve non-stop. That’s why brands resort to implementing telephoto capabilities with periscope cameras. They save space and don’t turn your phone into a mutant.

How does the periscope camera work?

TL;DR: Periscope cameras use a prism/mirror combo to reflect light 90 degrees and send it through lens elements onto the sensor. It’s used for magnification purposes.

If you can stomach a teardown of the iPhone 15 Pro Max when it becomes available, you’ll get to see what’s so special about a periscope camera: first of all, often it has a rectangular front element (which you can see even without the device being disassembled), unlike the other cameras (they’re circular). The iPhone 15 Pro Max, however, features a circular front element lens, not a rectangular. Very exotic.

In the periscope camera unit there’s a prism (or angled mirror) that reflects and redirects the light to the side. The light travels through the adjacent lens element and finally hits the sensor. Note that because of the orientation of the elements, the sensor is placed perpendicularly to the phone's back instead of in parallel. Think of it like that: if the ‘regular’ sensors face away from the back, the periscope one is facing the side buttons. Again, as with the rectangular front element of the lens, on the iPhone 15 Pro Max that's not the case and the sensor is indeed in parallel.

Of course, nothing is perfect and there are downsides. Yes, the periscope array is used in the name of compactness, but that’s in terms of ‘thickness’. This exotic camera uses a lot of inner space, just sideways, so in a smaller phone, some components and features ultimately have to be moved or removed in order to make room for the periscope. There are also possible issues like blurring and darkening the image because of the periscope optical scheme, but technology is advancing fast enough to minimize these problems.

Notable models with periscope cameras

Before we talk about some notable phone models putting in use the periscope camera system, as promised, here are the optical zoom monsters with protruding camera-like zoom lenses. Since you don’t see that design at all these days, you can safely assume they didn’t perform well at all (at least in US and Europe) in terms of sales and popularity. We’re talking about Samsung’s Galaxy K Zoom and the Galaxy S4 Zoom. Both devices offered 10x optical zoom lenses (24-240mm in terms of standard 35mm equivalent), xenon flashes, optical image stabilization and Samsung glass. Different sensors were put in the two devices, so there was a difference in the megapixel count: 16 vs 20.7 megapixels total.

The first mainstream device to embody a periscope camera is Huawei’s P30 Pro (2019), which brought to the table remarkable zoom capabilities. However, some remember the ancient times, and specifically 2004, when the Sharp 902 phone (which had 2x optical zoom) appeared and the internet claims it was the first mobile phone to incorporate a periscope technology in its camera setup. That’s impressive, given that the first camera phone had hit the market only a few years earlier.

Today the landscape is filled with periscopes. One can choose between Samsung Galaxy S23 Ultra (or the S22 Ultra, for that matter), Google Pixel 7 Pro (or the Pixel 6 Pro), Honor Magic5 Pro, OPPO Find X6 Pro and others.

And now, you get one in Apple’s newest maxed-out flagship: the iPhone 15 Pro Max. Choose wisely!