Knowing the difference between optical and digital zoom is important when shopping for a new phone. This isn't the only tech category where these two types of zoom appear, but here they collide like nowhere else. Do you want the one sentence version? Optical zoom uses magnifying lenses to allow you to get a much closer image of a scene than you see with your eyes. Digital zoom relies on software to achieve a similar effect. In almost all situations, the optical zoom is higher, but let's take a closer look at why.
Optical zoom in phones
Optical zoom on phones is completely different from what dedicated cameras use. Standalone DSLRs, mirrorless cameras, and compact cameras use a series of lens elements that move back and forth on the lens barrel to provide a harmonious tradition of focal lengths from their shortest. You can think of these lens elements as a series of magnifying lenses, and the camera sensor behind them as an eyeball (though of course our own eyes have a lens too). The phones use completely separate cameras for their different focal lengths. Although mobile phone cameras also have various lens elements in their "lens", they do not move. If a phone has, for example, a "normal" view, a very wide 0.6x view, and a 5x zoom, each has its lens and sensor. Only the software and processor are shared. Just look back at the Samsung Galaxy S4 Zoom to understand why this style is used. This phone-like camera had a traditional optical zoom, but it was much thicker than the other androids of the day. There isn't much demand for phones that are one inch thick.
Traditional optical zoom wouldn't work on a smartphone (Image credit: Canon) Zoom phones actually have two or three main lenses (without zoom in the traditional sense) with two or three different sensors. This may seem like a rather expensive way to get different views of a scene. But this also raises the question of how legitimate the term "lossless" is when used with these zoom cameras. Phone manufacturers sometimes use this term to talk about optical zoom. This tells you that digital "crop and zoom" techniques are not used. But it is potentially misleading. Do not forget that the quality of the photos depends entirely on the quality of the lenses and sensors used by your zoom camera. You could argue that there is a suggestion in "lossless" that enlarged photos will be of the same quality as non-enlarged ones. This is never really the case. Most zoom equipped phones use lower quality cameras at their 2x/3x/5x zoom. This is one of the main ways high-end phones count to improve camera quality. They usually have wide-angle and zoom cameras that don't downplay the quality of the lens and sensor. They may also have steeper zooms. The Oppo Reno 10x Zoom and Huawei P30 Pro models currently have the best zoom lenses in town.
The difference between the standard view and a 10x zoom on a camera phone (Image credit: Future)
Digital zoom on phones
Digital zoom is used when your phone does not have a lens/camera or you are trying to zoom in beyond the capabilities of this camera. The classic description of digital zoom is to crop an image and then enlarge the cropped segment to make it the same size as an image without a zoom. There is no extra detail in the source, so digitally zoomed photos tend to be blurry. Things get complicated again. The quality of digital zoom depends on several factors. At the lowest level, phones simply fit the image you see when capturing a standard photo, stretch the result to the same resolution as the original image, and apply a slight blur to hide jagged edges. Smarter processing used by high-end phones will interpolate the missing information. This is where an image processor looks at the pixels of the raw cropped image and tries to calculate the details that can be "seen" by a high-end camera sensor. As AI learning and imaging improves, this interpolation will improve. For example, if the camera can recognize the texture object it needs to render, it is more likely to create compelling "composite" details. This is especially true for tight textures like glass and foliage. Right now, you won't see a lot of that smart stuff on phones. Google is the leader in this field, largely because it's one of the phone makers that just wanted to put the camera on the back of its phones. Google goes even further with digital zoom with the Google Pixel 3 series phones. Enlarged images are created using a composite of multiple images, and the optical stabilization engine moves the images slightly. camera during capture. It is used to emulate the data that would be captured by a higher resolution sensor because this movement is so slight that it captures the details between the "real" pixels. That's what we call smart. Google calls this Super Res Zoom (and you'll find more about it in the video below). In our experience, this doesn't compete with the best optical zoom phones, but it performs better than some lower-end phones.Hybrid phones with zoom
And what about hybrid zoom? This is a term that phone manufacturers are more or less forced to use to describe enlarged photos that exceed or fall between the local lengths of the actual lenses. Sometimes this simply means that the digital zoom is used, for example to take a 10x image with a 5x lens. And, like digital zoom, this may involve a smoother filter or a smarter interpolation algorithm. Some other phones also use information from other cameras to help you. For example, if a phone has an 8 MP 2x 2x optical zoom and a 48-megapixel main camera, you can use the image data from both to create the final photo.
The periscope lens of the Oppo Reno 10X Zoom. (Image credit: Future)