Xiaomi Mix 4 Free-form Lens: How it Achieved Distortion-free Ultra-wide-angle Photos?

Xiaomi Mix 4 Free-form Lens

Xiaomi Mix 4 Free-form Lens

On the evening of August 10, Xiaomi introduced three year’s work: Xiaomi Mix 4. Among the many highlights of the device, the biggest highlight is the ‘CUP’ Camera Under Panel, which becomes Xiaomi’s first phone with an under-screen camera.

Today, Xiaomi officially detailed Xiaomi Mix 4 Free-form Lens characteristics and benefits. The Xiaomi MIX 4 uses a 120° free-form ultra-wide angle lens for the first time. By calculating the aberration of each field of view in the full image plane, each image point is corrected one by one to create a unique curvature of the lens, without algorithmic cropping, and straight out of the 120° ultra-wide field of view photos with almost no distortion.

Xiaomi Mi MIX 4 how to take almost distortion-free ultra-wide-angle photos?

The frequency of use of ultra-wide-angle lenses in mobile phone photography has gradually increased with the improvement of ultra-wide image quality. This is because ultra-wide-angle lenses can not only record more images but also have advantages in picture composition that other lenses do not have.

The ultra-wide-angle lens takes a more three-dimensional picture, and the layout of the front, middle and long-distance view can open up the space, highlighting the depth and layering of the picture, and the content is full but also more visually impactful.

The traditional ultra-wide-angle lens, due to the majority of fixed curvature of the rotationally symmetric aspherical lens, will produce up to about 20% of the distortion problem. For distortion correction, usually cell phones will use an anti-distortion algorithm, through the screen crop to achieve correction function, but then the problem is that the crop will lead to the loss of part of the wide-angle view so that the ultra-wide-angle lens to shoot the image of the sense of less impressive.

The Mi MIX 4 uses another hardware-level anti-distortion method to achieve distortion-free ultra-wide-angle shooting: free-form surface ultra-wide-angle lenses. The free-form surface lens of Mi MIX 4 is more flexible. By calculating the aberration of each field of view of the holographic image, each image point is corrected one by one, breaking the rotational symmetry, creating a unique curvature of the lens, without algorithmic cutting, and almost straight out Distortion-free 120° super-wide field of view photos, realizing hardware-level anti-distortion, realizing the best image quality large image area of ultra-wide-angle imaging.

Xiaomi Mix 4 Free-form Lens

Why does distortion occur?

In the use of ultra-wide-angle lens shooting, is not often encountered such a problem, shot down the building, the left and right end of the barrel-shaped expansion of the distortion phenomenon, as if to the straight building with a Haha mirror filter, this is the traditional ultra-wide-angle lens barrel distortion brought about by the problem.

This is because the traditional ultra-wide-angle lens is designed symmetrically according to the central axis, and the curvature of any point is the same under the same radius, similar to an inflated football. The symmetrical design of the central axis will lead to optical aberrations generated by different fields of view when the light passes through the lens.

How the free-form lens makes the Xiaomi Mi MIX 4 ultra-wide-angle lens almost aberration-free

The free-form lens of Xiaomi Mi MIX 4 is a combination of asymmetric, irregular, and complex free-form surfaces, more like a balloon filled with water, with the curvature changing continuously at the same radius, so it can control the aberration of light and freely distribute the light intensity in different field of view areas as much as possible, and even control the angle of light entry, deflection direction, and light range difference through human design, to suppress aberrations and finally present photos with only about 1% edge aberration, with the edge of the picture almost “horizontal and vertical” to restore the real world.

Ultra-wide-angle integration with Smart Fusion technology, combining wide viewing angle and high image quality

The ultra-wide-angle lens of Xiaomi Mi Mix 4 not only provides a wider viewing angle with hardware-level anti-distortion but also has an excellent central image quality. With ultra-wide mode enabled, in some scenes the main camera and ultra-wide will be enabled to shoot at the same time, merging the two photos into one picture with SmartFusion technology.

The center area of the picture is about 85° angle of view actually taken by the 108-megapixel main camera, while the edges are taken by the ultra-wide-angle lens, attaching the super-high resolution of the main camera to the middle area of the ultra-wide-angle, significantly improving the picture quality of the center area of the picture, ideal for taking pictures of large landscapes, architectural complexes, and other scenes.

The ultimate exploration is the most basic product definition of the Xiaomi Mi MIX series. On top of the hardware foundation, Xiaomi Mi MIX 4 is more concerned with the experience upgrades it may bring. In response to the long-standing problem of ultra-wide-angle distortion, Xiaomi MIX 4 achieves the perfect combination of no distortion and good image quality by adding free-form lenses with ultra-wide-angle integration with Smart Fusion technology, giving even ultra-wide-angle lenses an experience comparable to that of the main camera.


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