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12 May 2022

Should you ever use digital zoom on a mobile phone?

Find out why ‘digital zooming’ isn’t always what it seems, and how to make sure you're taking the best photos with a smartphone
Samsung S20

Picture quality can be the difference between a prized shot to last a lifetime and a pixelated mess that's quickly deleted.

Deciding how and when to zoom can make or break an image, and with mobile phone cameras needing to find workarounds to compete with dedicated cameras, there's a lot more to consider. 

We explain how to make the most of a phone's zoom functions and demystify manufacturers' often grandiose claims around phone camera and digital zoom capabilities, to help you choose the right settings to achieve that perfect shot. 

We've tested phones with seriously impressive cameras for as little as £250. Browse our mobile phone reviews to find one.

Mobile phone cameras zoom types explained

Mobile phone zoom levels can sound impressive: you might find a camera spec boasting 6X, 12X or even, such as the Samsung Galaxy S20, 100X magnification.

But not all zooming is created equal. There are actually two types of zoom that any digital camera can do:

  • Optical zoom, where the camera lens extends its focal length, drawing it physically closer to the subject with no loss in quality. 
  • Digital zoom, where the lens gets no closer to the subject, but the phone simply crops the image and artificially enlarges a part of the picture.

Mobile phones, which now come with lots of cameras in small clusters, employ both types of zooming in their native camera app. Phone camera lenses can't extend like digital cameras do, so instead you will have two, three or even four lenses with different focal lengths built into the phone to create different levels of optical zoom. 

Much of a phone's zooming potential is usually digital. But while digital zoom can be a nifty way to create a magnified picture without needing a specialist lens, it also creates irreversible quality loss. 

Anybody buying a mobile phone or fixed-lens camera, such as a compact camera or a bridge model, should be wary of this. 

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What is digital zoom?

Digital zooming is when a camera continues to pull closer to an image despite surpassing the maximum focal length of its longest lens. 

Digital zooming is essentially cropping the margins of your photo and enlarging the image to fill the frame, making it look like the camera zoomed in. 

This causes image quality to nosedive. To compensate for this, manufacturers have created algorithms which artificially enhance the image to make it look better, also known as upscaling.  

When upscaling an image using software, your phone may sharpen it or even look at the pixels in it and inject different pixels into parts of your photo to make it look better (known as interpolation).

A particularly complex form of digital zoom, sometimes called ‘hybrid zoom’, uses the same techniques but with added steps, such as having every lens in the camera taking an image at once and then merging them together to make a cropped, upscaled image look better. 

This is the two halves of digital zoom: cropping and processing. Neither of these happen with traditional optical zooming.

What is optical zoom?

This is where your camera lens is physically closer to your subject. There’s no quality loss when you bring your lens closer to your subject.

The drawback is that optical zooming requires your lens to extend outwards and this is only feasible up to a certain degree for mobile phones. 

To compensate, most mobile phones have clusters of different cameras together. Each one has a different lens, so you can swap between less and more zoomed without lenses actually moving. 

High-end digital cameras can zoom more freely, but you need to spend a lot of money to buy a lens that has a high focal length. This is called a telephoto lens and it can have a focal length of 60mm, or even longer.

For a brilliant dedicated digital camera with an interchangeable lens, or a superzoom lens built-in, then read our digital camera reviews and find a Best Buy model.

Why mobile phones use digital zoom

Mobile phones are ultra-compact with small lenses locked behind glass screens made of extremely durable glass, like sapphire or Gorilla Glass. 

A lens that extends outwards extensively simply doesn’t fit into the design of a modern smartphone. 

Attempts have been made in the past to make camera phones that work like compact cameras, most notable the Samsung Galaxy S4 Zoom. 

This large smartphone had a large lens jutting out its back. It has a shutter button on its shoulder and it was 15mm thick. 

It didn’t catch on - and looking at it, it’s easy to see why. Phones have good cameras integrated into them now, but it’s unlikely they’ll use the same hardware as dedicated cameras anytime soon. 

If you're a beginner photographer, read out guide on how to shoot and edit photos like a pro to get a head-start.

Should I ever use digital zoom?

Undoubtedly - but it’s best to know you're using it. If the quality of your photo is ruined because you used digital zoom extensively, you’ll never be able to restore it. 

In contrast, if you take a picture without stretching it out, you can crop it later and zoom in using an image editor without losing the quality of the original image.

But there are scenarios where it’s worth using:

  • In moderation. If you magnify one or two steps beyond the maximum optical zoom, you’ll lose some quality but your phone’s upscaling should compensate somewhat. 
  • When you need a telescope. Zooming in to see something afar on your phone screen can be a great life hack, and if you’re not actually snapping a shot, then it doesn’t matter. 

But there are also times where it’s worth sticking to your maximum optical zoom length:

  • When quality is paramount. Cameras have gotten a lot better at upscaling blurry shots, but a picture taken in full resolution will always be superior. 
  • When you can edit your image. You can crop and enlarge an image after the fact. You can also do your own post-processing, such as sharpening your image, using editing software. 

If you want to shun digital zooming and edit your pictures yourself, then read our guide to the best Photoshop free alternatives and free photo editing apps.

Understanding manufacturer claims

If you’re buying a mobile phone, the good news is that you can always find out how much of a camera’s zoom is optical and how much is digital by looking at the specification.

We found that the biggest phone manufacturers were consistent when it came to publishing optical zoom options, even where further magnification is possible with digital zooming.

Some manufacturers have taken to a new term called ‘hybrid zooming’. This has a meaning that’s difficult to pin down, but it’s essentially a form of digital zooming.

Hybrid zooming can involve more complexity than digital zooming, such as the camera taking multiple images with its different lenses and compositing them, but specifics vary across manufacturers.

But in essence, it is fundamentally different from optical zooming and if you want the best form of quality for your photos, you should stick to heeding the focal lengths of the lenses on the phone. 

New names confound users

We found that manufacturers tend to create new terminologies for zooming when trying to sell new products. 

Samsung advertises the S20 as having ‘Super Resolution Zoom, a digital zoom that’s enhanced with AI’, but algorithmic upscaling is not a novel concept. In essence, it’s just the S20’s own application of digital zoom.

The S20 and S20+ have something called ‘Space Zoom’ which is ‘the combination of 3x Hybrid Optical Zoom and 30X Super Resolution Zoom’. In other words, the maximum optical zoom and then digital zooming afterwards.

There’s no doubt that upscaling algorithms are getting better. But when it comes to knowing what hardware you’re buying, the actual optical length is still the best and most dependable guide. 

If you want help on buying a new mobile phone, read our guide to the best mobile phones for 2022 to see our expert buying advice.

Camera apps obscure the difference

Although manufacturers usually make these distinctions in their marketing, it remains the case that camera apps obscure the difference between optical and digital zooming.

The iPhone 13 family, for example, allows you to switch between three lenses when you open the camera app: 0.5X, 1X and 3X magnification (a wide-lens, a human field of vision, and a close-up perspective).

But by using your fingers to zoom manually, you can scroll up to as much as 15X magnification without any notice that you’re effectively just cropping an upscaled image obtained with the 3X lens. 

This means that most of the possible zooming available on the phone is artificial with no indication when you’ve swapped from optical to digital zooming. 

This is incredibly common. Oppo shows you what this looks like on its article about the Reno’s ‘hybrid zoom’.

Read our news story on three things a digital camera can do that your smartphone can't to see where dedicated digital cameras pull away from mobile phones for photography.

Camera specs to look for when you’re buying a mobile phone.

If you care about your phone’s camera performance, look for these things:

  • The size of its sensors. This is the single most important feature that determines picture quality. The bigger the better. 
  • The focal lengths of its lenses. Don’t just look for the cameras with the longest (telephoto) lenses, wide-angle lenses are also helpful for scenic shots and panoramas. 
  • Shooting options. The more control you have, such as a portrait mode to blur the background or a long exposure mode for low-light shots, makes your shooting more versatile.
  • Optical image stabilisation to reduce the impacts of shaking when you take stills and video. 
  • HDR mode. This takes your photo in different exposures and merges them to create a picture with a large range of colours in it. This is great for balancing very bright or very dim shots.