Zoom power is getting more and more attention when talking about smartphone camera specs. With brands like Samsung, Sony and Huawei disrupting the market with devices with insane zoom capabilities, optical and digital zoom are some of the words floating around.
But what do they mean exactly? What is the underlying technology that powers each of them? How does this affect the quality of images your smartphone camera can produce? And which of them should you look for in a smartphone?
What is zoom on smartphone cameras?
In smartphone photography, zooming is simply a way to magnify an object of interest in front of the camera or make it appear closer. Of course, in a more general definition, zooming also covers a way of reducing the appearance of an object to make it appear farther away than it actually is. This is why you will often hear terms like “zoom out”.
However, most people don’t care how much their smartphone camera zooms out; they mostly care how much it can zoom. So let’s focus on the “zoom in” side of things. But how exactly does the zoom work?
Whether it’s a DSLR-type camera or your smartphone camera, zooming is achieved by varying or adjusting the focal length of your camera. Focal length is the distance from the image sensor in your smartphone camera to where the light converges and focuses the image.
The longer the focal length, the greater the magnification. Conversely, a shorter focal length gives you more angle of view but less magnification. If you want to know more about focal length, we have already done a detailed introduction to focal length in photography.
In traditional photography, one way to zoom is to swap out your lens for one with your preferred focal length. Alternatively, you can use zoom. A zoom lens allows you to mechanically adjust or increase your focal length to achieve magnification, or simply zoom.
Unfortunately, zoom lenses tend to be bulky. To house the mechanical arrangements of components and parts needed to build a true zoom lens, your phone would be thick and heavy and have an unsightly camera bump. At a time when consumers yearn for slim and sleek phones, the massive camera bumps would be a no-start.
Nevertheless, zooming in should be done on smartphones. But how?
Optical zoom in smartphone photography
Optical zoom is the proper form of zoom in which the moving parts of a camera lens are mechanically adjusted to increase its focal length to achieve magnification. Optical zoom is “zoom as zoom was meant to be”. Unfortunately, zoom lenses that can adjust their focal length are not yet a thing on smartphones, so optical zoom in smartphones is achieved by switching between cameras of different focal lengths.
Unlike DSLR cameras, the optical zoom of smartphone cameras is not achieved by the actual movement of mechanical parts to adjust the focal length. Instead, when you want to use 2X zoom, your smartphone will switch to another camera that matches the focal length needed to achieve that zoom power. If you’re wondering why many modern smartphones come with multiple cameras, this is one of the reasons.
So each camera has a fixed focal length, some shorter, some longer. Your smartphone simply switches to the lens with a longer focal length to give you a zoom. This is why some experts refer to the version of optical zoom on smartphones as multi-camera zoom. Nevertheless, optical zoom is the “true form of zooming” and delivers similar results to what you would get if you got closer to the subject.
Although the lens or camera swap technique used in smartphones works, there is a small problem. Since the cameras do not use zoom which gradually adjusts the focal length, continuous zooming is not possible on almost all smartphones.
This means that if your smartphone comes with multiple cameras that have a fixed focal length of up to 2x, 4x and 5x optical zoom, when zooming, the actual optical zoom level just changes from 2x to 4x and then to 5x when the cameras are switched. Anything in between, like 3x or 4.5x zoom, for example, is achieved through digital zoom.
But what is digital zoom?
Smartphone digital zoom photography
Digital zoom is a software attempt to reproduce the results of optical zoom. In digital zoom, there is no real change in focal length. The camera simply takes the image in front of it, crops a section, and enlarges the cropped section to fill the available display frame. Digital zoom is less real zoom and more brilliant cropping technology.
Since digital zooming involves cropping, the resulting image usually has a noticeable loss in quality. Suppose you have a smartphone with a 20MP camera and you want to perform 2x digital zoom. What happens is that your smartphone camera will grab the image at 20MP resolution, lock onto a 10MP portion of the image containing the object you want to zoom in on, and then crop the image. another 10MP.
The 10MP portion containing the object of interest is stretched to cover the frame, often resulting in pixelation and an overall loss of quality.
So if your phone offers 2x and 5x zoom, anything in between is probably handled digitally or using a hybrid approach called hybrid zoom. Hybrid Zoom combines optical and digital zoom data using computer photography to create magnified images beyond the true optical capabilities of a lens.
What type of zoom should you be looking for?
Often, smartphone manufacturers advertise their products with labels such as 20x zoom or 60x zoom. Sometimes a catchy name is added. Samsung has 100x Space Zoom. Unfortunately, most of these labels are just marketing gimmicks.
Before you get excited about the power of zoom, you have to ask yourself, “How many real optical zooms?” Of course, smartphones like Samsung’s Galaxy S series have admirable digital zoom power. This is possible thanks to large sensors and many megapixels, which gives them more resolution to work with.
However, the digital zoom is still cropping. Optical zoom is what provides true magnification and it is the best form of zoom you should look for in a smartphone. Some smartphones with impressive optical zoom include the Sony Xperia 1 IV, Samsung Galaxy S22 Ultra, Vivo X80 Pro, Pixel 6 Pro, and iPhone 14 Pro Max.
Zoom power isn’t as easy as it looks
Although some smartphone manufacturers talk a lot about the zoom capability of their smartphones, the zoom capabilities are not as simple as they seem. More zoom is not necessarily better; it depends on the type of zoom and the underlying technology that powers it.
Never buy one smartphone over another because it has a bigger zoom power label. 5x zoom might be better than 10x zoom. True zoom power isn’t about how many times a camera zooms. It’s about how much your camera can adjust its focal length and the power of the underlying software that can help it improve image magnification beyond its optical capabilities.