The difference between optical zoom It is digital zoom is that the first uses a set of lenses to generate a real approximation, favoring image quality. In digital, the approximation is made by software. Next, understand how the types of zoom work, their advantages and limitations.
How optical zoom works
O optical zoom “TRUE” is a mechanical process that moves the camera’s internal lens assembly to generate a wide focal length.
The greater the focal length applied to a zoom lens, the closer the photographed or filmed subject is.
In the context of DSLR and mirrorless cameras, optical zoom lenses (zoom lenses), have minimum and maximum focal lengths. This feature makes them different from fixed lenseswhose focal length never changes.
To allow the focal length to be shortened or lengthened, a telephoto zoom lens relies on an array of variably shaped lens elements, as shown in the image below.
According to the applied control, the lens elements change position in order to create an image enlargement effect. Then, the light captured by the lens goes towards the image sensor for the photo or video to be finally generated.
Cell phones can also offer optical zoom, but in a limited way. Therefore, some models have hybrid zoom, a method that combines lens approximation with digital zoom (magnification made by software) to generate an artificially greater range.
How does optical zoom work on mobile?
As cell phones are compact devices, there are physical limitations to moving the lens. Therefore, many smartphones use multiple cameras with different focal lengths to apply optical zoom.
This is the case of the Samsung Galaxy Z Fold 4. The device has a telephoto lens with a focal length three times greater (3x) than the main camera. Thus, if the user activates the 3x option in the photo application, the zoom camera is triggered instead of the default camera.
In 2022, Sony introduced the first “real” optical zoom phone: the Xperia 1 IV. The model has an optical assembly with a focal length of 85-125 mm that allows zooming from 3.5 to 5.2x in relation to the 24 mm wide-angle camera also present there.
Some smartphones, like the Galaxy S22 Ultra and the Motorola Edge 20 Pro, bring a periscopic camera for optical zoom. This system overcomes the lack of internal space by positioning the lenses perpendicular to the cell phone.
Advantages and limitations of optical zoom
Optical zoom is often considered better than digital, but it also has its limitations. You can expect the following features:
- Higher image quality: image composition with optical zoom does not cause loss of sharpness, contrary to what can happen with digital zoom;
- Does not depend on the sensor: Optical zoom does not require a high megapixel sensor to generate sharp images;
- Wide scalability: some zoom lenses have so many levels of approximation that they can reach subjects tens of meters away;
- physical limitation: on cell phones, the optical zoom is quite limited because there is not enough space for the distance of the lenses. Zoom lenses for DSLR and mirrorless cameras can be bulky and heavy;
- High cost: Optical zoom is expensive to implement because it is based on a set of sophisticated physical components. On DSLR or mirrorless cameras, zoom lenses can cost thousands of dollars.
How digital zoom works
Digital zoom uses software features to crop the image. Then there is an enlargement of the cropped area.
This solution is implemented in mobile phones and simple digital cameras to compensate for the lack of optical zoom.
However, digital zoom decreases image quality as the magnification increases. This is because when the crop is enlarged, gaps appear between the pixels.
To fill these spaces, the software performs an interpolation, that is, it creates pixels from those that form the original image. Pixel interpolation decreases sharpness and, if too intense, generates a pixelated image effect.
Quality loss with digital zoom can be mitigated or avoided if the magnification is applied to a high resolution image. In this case, the amount of pixels resulting from the interpolation is not large.
We shot the following images with the 50-megapixel camera on the Samsung Galaxy A54. The second photo has a 2x digital zoom compared to the first. As the image resolution is high and the magnification has not been exaggerated, the loss of quality is almost imperceptible.
The photos below show the zoom being applied to a car. Notice that in the second photo, the magnification level was so high that it lost sharpness.
Advantages and limitations
Digital zoom can be the best solution for those who have portable equipment and do not need very high resolution images. You can expect the following features:
- Deployment on small devices: digital zoom is a solution for portable equipment that, due to size limitations or cost control, does not have optical zoom;
- Easy to use: digital zoom can be applied with specific buttons on the cameras or with pinch gestures on the smartphone screen;
- High magnification capacity: the digital zoom can generate a high approximation effect, mainly in cameras with more megapixels, even if the excess can impair the image quality;
- Possible loss of sharpness: Pixel interpolation can cause noise and decrease image definition. Not exaggerating the level of crop or magnification prevents the loss of sharpness from being accentuated.
Hybrid Zoom: Combining features on smartphones
Hybrid zoom is a method that uses digital zoom to enlarge an image captured with optical zoom. This approach is useful when the goal is to get closer than that achieved with a telephoto lens.
This is the case of cell phones that promise 100x zoom to allow a photo of the moon. The Samsung Galaxy S23 Ultra is one of them. The device has a periscope lens with 10x optical zoom, but a spatial zoom mode uses software to extend the range up to 100 times.
Phones like Huawei P50 Pro and Xiaomi 10 Pro were also launched with 100x hybrid zoom.
