Except for a few products such as Sony Xperia 1 IV, Samsung Galaxy Zoom, and Asus ZenFone Zoom, the majority of cell phones have an “optical zoom” that actually switches between cameras. In a multi-camera phone, there is an image sensor behind each lens, and when you switch the magnification, both the sensor and the lens change. This situation is different from both the optical zoom of a camera lens and the changing of a different lens on a DSLR/MicroSD.
So, the “optical zoom” on the phone is precisely a “relay” of multiple fixed-lens cameras with digital processing.
The telephoto lens on the Sony Xperia 1 III / 5 III can be switched between 70mm F2.3 and 105mm F2.8. It can be called a dual focal length, but it is not a real optical zoom.
Learn more About magnification
- The vast majority of phones set the 23-27mm focal length to 1x (1.0x), so 0.4x, 0.5x, 0.6x for ultra-wide and 2.0x, 3.0x, 5.0x for medium telephoto …… But this poses two problems.
- The definition of 1x is not the same, so 0.5x, 3x, 5x on different phones differ in terms of viewing angle.
- When a phone advertises a 10x zoom capability, it can be interpreted as if it has a 10x telephoto camera, or it can be interpreted as if it is a 10x zoom from ultra-wide angle to telephoto (e.g. 0.5x – 5.0x).
- So, instead of caring how many times the lens is, just check/calculate what the equivalent focal length really is.
Intermediate focal lengths
Between two fixed-focus cameras (e.g. from a 1.0x wide-angle prime to a 3.0x telephoto), intermediate focal lengths can be handled in several ways.
The initial approach was digital zoom, which resulted in a steady decline in image quality from 1.1x to 2.9x; then a significant improvement in image quality when going from 2.9x to 3.0x.
After that, Android phones generally began to add “picture fusion” technology, for example, at 2.9x, 1.0x and 3.0x cameras will be called to take pictures at the same time, using the 1.0x outer circle picture to make up for the 2.9x and 3.0x angle of view gap. (This method is only applicable to taking pictures)
Finally, since most phones today use a Quad Bayer sensor as the 1.0x wide-angle primary camera, it can output 4x pixel photos in high pixel mode. So many phones that focus on imaging will take a high pixel shot at 2.0x focal lengths and then capture the center area to achieve the zoom effect (e.g. shoot in 48MP mode and then take the middle 12MP, which is equivalent to a 2x zoom) – this operation is sometimes advertised as “lossless zoom”.
▲ Diagram of fusion zoom, from DXOMARK
Automatic switching
Even cameras with 2.0x and 3.0x telephoto focal lengths sometimes automatically switch to shooting with the main camera or even ultra-wide angle. Reasons for this include subjects exceeding the closest focusing distance, low ambient light, and inability to support the selected video shooting format.
Intermediate focal lengths
The physical specifications and software settings of cell phone cameras are already somewhat complex, and the addition of technologies such as screen fusion and quad-bayer make the working state of cell phones more diverse. For most users, we don’t need to delve into how the phone actually works after selecting zoom in the photo interface; but for those who value images and have some requirements for image quality, they still need to see the official propaganda and read some analysis articles to understand the best working mode of their phones.
But those who value images and have some requirements for image quality, still need to read the official propaganda and read some explanation articles to understand the best working mode of their phones.
