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Optical vs. digital zoom: What you need to know

Some camera features are worth paying for, while others seem to exist exclusively to print big numbers on the box to sway naive buyers. When it comes to zoom — whether on a smartphone or a camera — one type of zoom is actually worthwhile, while the other only artificially inflates the camera’s feature list.

Optical and digital zoom are two very different ways to snap a closer photo without moving your feet. Optical zoom — the only zoom that’s really worthwhile — means the camera can zoom using physical lens parts, while digital zoom means the camera uses software to “zoom.”

Now that the camera in your smartphone can boast either type, understanding the differences between optical and digital zoom can help you decide which device to buy, and it can also help determine how you shoot with the gear you have.

What is optical zoom?

A close-up of the moon taken with the 125x optical zoom on the Nikon P1000. Image used with permission by copyright holder

Optical zoom is created by moving the physical glass within a lens. Depending on how the glass elements are arranged, the lens will capture a wide angle or bring distant objects up close.

With the lens itself magnifying the view, optical zoom does not affect a photograph’s resolution — all of the pixels on the sensor still get used.

The millimeter number on a lens indicates the focal length, and the longer the focal length, the more “zoomed-in” the lens is. A 24mm, for example, is a wide-angle, while a 300mm is a telephoto.

The X rating on a device, such as 3x, 10x, or 83x, indicates the zoom multiplier, but not the actual focal length range. A 3x zoom lens, for example, can capture a photo that’s 3x farther than its widest angle, but it doesn’t tell you what that widest angle is.

What is digital zoom?

Digital zoom doesn’t use physical lens elements to get a closer shot. Instead, the software “zooms” electronically. Contrary to what CSI would have you believe, you can’t add resolution to a photo with a magical zoom-and-enhance function. Essentially, digital zoom is no different than if you cropped the photo in post.

Because a cropped image tosses out pixels, digital zoom reduces resolution and image quality. Images start to get less detailed, less sharp, more pixelated, and noisier once you start using digital zoom. 

Digital zoom isn’t really a feature that should be considered as a bonus to any camera or smartphone, because you can do the same exact thing by opening the photo in an editing app and cropping closer.

What is a hybrid zoom?

Some manufacturers list a specification for a hybrid zoom — this is simply using the optical zoom and digital zoom together. If you use a 10x optical zoom and mix that with a 2x digital zoom or crop, you get a 20x hybrid zoom. While a 20x hybrid zoom is better than a 20x digital zoom, image quality still degrades with the digital part of that optical-digital mix.

How your phone zooms

Image used with permission by copyright holder

Smartphones don’t have much space for lenses equipped with optical zoom, but a few manufactures have found ways to still cram optical zoom into a smartphone — or even compensate with software.

Just a few years ago, smartphones only had digital zoom. Paired with a tiny sensor, zooming in with a phone quickly became a pixelated mess. Some devices have now incorporated multiple lenses covering different focal lengths, while companies like Google have used computing algorithms to make up for the physical hardware that can’t fit inside a phone.

Using multiple lenses isn’t true zoom, however. Instead, it’s similar to swapping in different prime lenses on a DSLR. To imitate the appearance of a zoom lens, phones use digital zoom to transition from one lens to the next in a way that is mostly invisible to the user. This does mean that some quality is lost in these in-between stages. To maintain the highest quality, always manually select the lens.

Huawei found a workaround for those size limitations, however, incorporating a 5x zoom lens in the P30 Pro. How? The lens is actually oriented the wrong way, down the length of the smartphone instead of the narrow width. These folded optics use a mirror, so that, despite the lens running the wrong way, you still point the rear of the smartphone to snap a photo.

And just like smartphones have used computing power to make up for a lack of background blur, the device’s computing power can help make up for the lack of zoom, too. Google’s Super Res zoom is technically a digital zoom, but it captures a result that’s much closer to a 2x optical zoom than a 2x digital zoom.

How? The feature, introduced on Google Pixel 3 models, captures several photos instead of a single photo and stitches them together. That increases the resolution, so the loss of detail that zooming in creates is much less noticeable. Capturing several photos isn’t ideal for moving subjects, but it creates a digital zoom that actually doesn’t look horrible.

Zooming into the future

When it comes to dedicated cameras, don’t be fooled by grandiose digital zoom claims. Stick to optical zoom.

It’s a different story with phones. Here, digital zoom is often unavoidable, given the size constraints of the device. This has forced companies to invent novel ideas to get around the usual limitations of digital zoom, technologies that will only improve going forward.

Artificial intelligence is also being used to improve image upscaling, which could also lead to better digital zoom in the future. For now, however, there’s only one true type of zoom that’s worth paying for, and that’s optical.

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