A periscope lens (periscope) is used in smartphone cameras to provide increased optical zoom capability. Its periscope-inspired structure is suitable for the thin thickness of a cell phone and can achieve a wide focal length, favoring image quality.
How does a periscope lens work?
A periscopic lens is made up of optical elements that move to decrease or increase the focal length, just like conventional zoom lenses. The greater the focal length, the greater the zoom, that is, the farther the camera can look for the subject (person, animal or object to be photographed or filmed).
The difference is that the Periscope lens has a structure parallel to the body of the apparatus to allow its optical elements to move. In common lenses, this structure is vertical and designed to come out of the camera.
In a periscope lens, the optical elements move horizontally rather than projecting out of the scope. Therefore, the thickness of the smartphone increases little or not at all.
To generate the image, a prism or mirror mechanism inside the camera “bends” the light entering through the external lens at a 90-degree angle. This beam passes through the optical elements, positioned according to the desired magnification, and reaches the image sensor.
A periscope lens provides up to 10x optical zoom, typically. Some smartphones, such as the Samsung Galaxy S23 Ultra, extend this capability by applying hybrid zoom, that is, they use digital zoom (generated by software) to enlarge an image generated with optical zoom.
Many cell phones complement the periscope lens with autofocus and OIS (optical image stabilization) to help the user not to take blurry or out of focus pictures.
Periscope vs Telephoto: What’s the Difference?
Generally speaking, a telephoto lens is a lens with a focal length equal to or greater than 85 mm. Thus, a periscope lens can be considered telephoto if it has a long focal length. See in detail the differences between periscope, telephoto, macro and more cameras used in smartphones.
Advantages of Periscope Cameras
In addition to allowing a cell phone to accommodate an optical zoom mechanism without increasing its physical size, periscopic cameras offer advantages such as:
- variable range: the approximation of a periscopic camera varies between 5x and 10x. High zoom levels can affect sharpness, but not to the point where there is a significant loss of image quality;
- Versatility: the periscope mechanism may allow the cell phone to record images unreachable on smartphones with common cameras, such as photos of the Moon;
- Zoom without changing lenses: Periscope cameras achieve different zoom levels with the same lens. Cell phones without this feature change the main camera for another with a longer focal length to zoom in;
- Adjustable zoom while recording: the periscope mechanism allows you to enlarge or reduce the field of view without having to stop filming;
- Macro shots (without macro lens): Periscope cameras can also be adapted to record detailed photos of insects, plants and very small objects, even if the cell phone does not have a macro lens.
Disadvantages of periscope lenses
- limited optical zoom: the zoom of a periscope lens is normally no more than 10x. It’s an interesting level of closeness for a cell phone, but it doesn’t surpass the reach of DSLR or mirrorless camera lenses;
- Increased chance of noise: Periscope lenses tend to have a wide lens aperture, which can result in grainy images in low-light environments. Many smartphones fix the problem via software;
- light reflections: Lights can be reflected more easily in periscope lenses. In some situations, the entire field of view is too bright. Manual and automatic adjustments avoid the problem;
- high price: Periscope cameras are more expensive than conventional ones, so they are usually found only in premium smartphones.
The first cell phone with a periscopic system for the camera was the Sharp 902, launched in 2004. However, the technology only reached smartphones years later: in 2015, Asus launched the Zenfone Zoom with a periscopic camera and 3x optical zoom and, in 2017, Oppo presented a prototype that allowed 5x optical approximation.
The periscope camera started to appear in more premium phones starting in 2019, with the arrival of the Huawei P30 Pro. In the following years, Samsung, Xiaomi and Oppo itself launched cell phones with the feature. Examples are the Galaxy S22 Ultra, Xiaomi Mi 11 Pro and Oppo Find X6.