Over the years, the development of mobile imaging has evolved significantly. Despite the familiarity with some technologies and concepts, many netizens still harbor misconceptions. Hopefully, the following content can help dispel confusion and clarify the truth.
Currently, the optical zoom on most phones essentially involves multiple fixed-focus cameras working in tandem. Each lens corresponds to a sensor. Typically, the sensor size of the wide-angle camera is the largest and is regarded as 1x in phone zoom; the sensor sizes of other cameras, which are smaller, represent zoom multiples: for example, the 14mm ultra-wide-angle compared to the 23mm wide-angle is around 0.6x, and the 120mm telephoto compared to the 23mm wide-angle is around 5x.
Aside from fixed-focus lenses, regardless of the optimization algorithms utilized, it essentially amounts to digital zoom. However, I do not believe that phones need to implement true optical zoom (like the Sony Xperia 1 IV)—the fundamental contradiction in mobile imaging lies in the amount of light admitted, which the structural constraints of periscope optical zoom modules cannot fully address due to sensor size and lens aperture limitations.
TIPS: Focal length ratio over zoom level
In mobile imaging, there is no unified standard for zoom level. Currently, most manufacturers choose 23mm or 24mm as 1x; Huawei and Honor designate 27mm as 1x and defaultly crop the wide-angle and telephoto according to this configuration. Therefore, under the same zoom level, different brand phones may exhibit significant differences in field of view.
Therefore, it is crucial to focus on the effective focal length.
Currently, products like Xiaomi 14 Ultra and OPPO Find X7 Ultra feature a quadruple rear camera setup with ultra-wide-angle + wide-angle main camera + mid-range telephoto + telephoto, while products like Vivo X100 Ultra and Huawei Pura70 Ultra opt for a triple rear camera setup with ultra-wide-angle + wide-angle main camera + telephoto.
The core difference between the two approaches lies in the presence of either dual telephoto lenses or a single telephoto lens. The advantage of dual telephoto lenses is the ability to cater to portrait (70-90mm) and far-telephoto (120mm and above) photography needs, but the downside is the increased space consumption, which affects battery life and overall device ergonomics. In contrast, a single telephoto lens helps save space, lower costs, but it is challenging to address the entire range from mid-range telephoto to long telephoto—brands like Honor and Vivo opt to enhance far-telephoto capabilities of a single telephoto lens through billion-pixel sensor technology, which is a promising direction.
TIPS: Balancing focal lengths
In the limited spatial confines of a phone, each camera module must cater to a wide range of subjects. It is more beneficial to have a high-quality 5x telephoto camera that can mimic 10x zoom, rather than incorporating another 10x telephoto camera. Similarly, utilizing a 1-inch large sensor main camera with an effective focal length of approximately 23mm to accommodate shooting at 28mm and 35mm is more versatile than replacing the main camera with a slightly smaller sensor size designated as 35mm fixed-focus.
Why not eliminate the ultra-wide-angle lens? Perhaps for many photographers, the creative value of ultra-wide-angle photography may be limited. However, for numerous users, the ultra-wide-angle lens plays a crucial role in recording moments. Furthermore, the ultra-wide-angle lens serves essential functions in depth-of-field simulation at certain focal lengths, as well as ensuring uniform white balance in multi-camera setups.
Since the release of the Huawei P20 Pro, mobile cameras have ventured into the realm of tens of millions, even exceeding one billion pix els. The vast majority of 30 million and above sensors incorporate quad-bayer (or nona-bayer, hexadecagon-bayer) structures. Typically, neighboring pixels of the same color operate in a merged manner for the realization of equivalent large pixels.
Consider a common scenario: a 50 million pixel sensor with quad-bayer structure, individual pixel size of 1μm, and approximately 50 million effective pixels. In most scenarios, the merging of four pixels equates to an effective size of 2μm, resulting in an actual output of around 12.5 million pixel photos. Only in high-pixel mode, through pixel rearrangement algorithms and optimizations, can photos of around 50 million pixels be produced, facilitating the capture of more intricate details and offering greater cropping flexibility.
Multi-bayer sensors not only cater to marketing demands but also contribute to improving dynamic range (single-frame HDR), autofocus (2×2 OCL), and digital zoom (ISZ) quality—the prevalent In-Sensor-Zoom (ISZ) sensor-scaled zoom that crops the central 1/4 region of the sensor can be likened to switching to high-pixel mode before capturing an image. However, transitioning to high-pixel output often limits the shooting mode, and due to computational and power constraints, cannot match the image quality of merged outputs.
TIPS: A positive trend
Within the iPhone 15 series, Apple offers an option to combine 12 million pixel standard photos with 48 million pixel high-resolution mode photos to produce 24 million pixel photos. Seven months later, Huawei also incorporated a similar feature in the Pura70 series (another brand is confirmed to introduce a similar feature through a firmware update). It is foreseeable that with the continual enhancement of mobile chip computational capabilities, breaking through the 12/12.5 million pixel threshold in daily photography will soon be achievable.
For any imaging device, optics play a crucial role. Improving optics, be it enlarging the aperture of wide-angle cameras, enhancing the close-up capabilities of telephoto lenses, or reducing lens flares, necessitates optical enhancements.
However, with the limited dimensions of phones, in many flagship camera systems, camera modules occupy the most significant space within the device, second only to the battery and screen (larger than the actual area of the motherboard). Thus, the scope for optical improvements remains restricted. To further enhance photographic capabilities, particularly telephoto performance, reliance on optimized algorithms, including AI-powered image prediction, becomes imperative.
Collaborations between domestic phone manufacturers and Leica, Zeiss, and Hasselblad provide technical support in imaging styles and shooting experiences, rapidly elevating brand recognition in overseas markets. Leveraging the assets of international brands facilitates the creation of practical and user-friendly shooting features (such as the Zeiss lens flare simulation on Vivo phones).
However, it is imperative to realize that these foreign brands do not directly partake in optical design or lens manufacturing; they provide authorization and certification. Ultimately, they remain external entities. Looking ahead, it is crucial for us to establish and cultivate our own imaging brand—the era of mobile photography belongs to Chinese enterprises.
Ther e are often queries as to why domestic phone manufacturers do not venture into producing cameras devoid of phone functionalities.
Firstly, the camera market is niche, with far lesser scale and profit margins compared to smartphones.
Secondly, the primary advantage of smartphones over cameras lies in their portability and swift sharing capabilities. Omitting phone functions would essentially entail self-imposed limitations.
Lastly, current mobile imaging hinges on refining hardware and perfecting algorithms within a confined space. Discarding the smartphone form factor would entail engaging in sensor size and optical performance competitions, which are not the forte of phone manufacturers.
In conclusion, leave the business of manufacturing cameras to companies like DJI.
Article Source: WeChat Official Account: 相机笔记 (ID: xjbiji) | Author: 滕飞et