Track Hyper | Xiaomi MIX Fold 4: Can it compete in terms of slimness and imaging capabilities?

Author: Zhou Yuan / Wall Street News

Guided by the principle of "experience first", Xiaomi once again iterates its foldable phone with the "thin + performance" label. Among them, "performance" has always been a traditional focus of Xiaomi phones, while "thinness" is moving closer to the current trend in the foldable phone industry.

On July 19th, Xiaomi released its thinnest and lightest foldable phone to date - Xiaomi MIX Fold 4: the folded body is as thin as 9.47mm, and when unfolded, it is only 4.59mm thin, setting a new record for the thinnest body of Xiaomi foldable screens. The total weight of the device is 226g, on par with Huawei Pura 70 Ultra and Honor Magic V3 (foldable phones).

This is the technological achievement of Xiaomi's foldable screens after four years and the release of three generations of products.

On April 25th, IDC released a report stating that foldable screens are gradually addressing issues such as being heavy, not durable, poor battery life, significant gaps in imaging compared to flat screens, and high prices. The resolution of these issues signifies that the technology and user experience of foldable screen phones are further maturing, becoming a replacement for high-end flat flagship phones.

Since its establishment, Xiaomi's flagship phones have never disappointed the market in terms of performance. Starting from the Leica joint imaging collaboration in the Xiaomi 12S series, this collaboration has now extended to foldable products: Xiaomi MIX Fold 4, the first to feature Leica Summilux optical lenses, achieving a full focal range quad-camera setup, with the main sensor equipped with the Light Hunter 800.

Compared to Honor Magic V3 and vivo X Fold 3 Pro, which also focus on "thinness" and "imaging", Xiaomi MIX Fold 4, does it have the strength to compete?

Who is the Thinnest: Experience First

From the release of the first foldable flagship MIX Fold in March 2021 to the launch of the new Xiaomi MIX Fold 4 on July 19th this year, Xiaomi's foldable phones have gone from experimentation, to "breaking the last kilometer of foldable screens" (MIX Fold 2), to "defining a new standard for the second half of foldable screens" (MIX Fold 3), and now to setting a new "thinness" record in the past three years with this generation (MIX Fold 4).

In fact, Xiaomi was the first to notice that the "thinness" experience of foldable phones would become the main direction of future consumer demand. When Xiaomi released MIX Fold 2, it had already noticed this trend and achieved a folded thickness of 11.2mm and an unfolded thickness of 5.4mm, establishing the industry's direction towards achieving a "thinner and lighter" foldable body as the correct path that foldable phones need to strive for through technology solutions On July 19th, Xiaomi's founder, chairman, and CEO Lei Jun delivered his fifth annual personal speech in Beijing with the theme "Courage". Following that, Xiaomi launched the MIX Fold 4, which set a physical standard of "9.47mm (folded state)/4.59mm (unfolded state) and 226g weight", making it the "most advanced, precise, and thinnest flagship with full configuration" in the history of Xiaomi smartphones.

Wall Street News listed the rankings of the "thinness" (folded state, unfolded state, and weight) of the new generation large folding phones in the industry: Honor Magic V3 with dimensions of 9.2mm, 4.35mm, and 226g; vivo X Fold 3 Pro with dimensions of 11.2mm, 5.2mm, and 236g; Huawei Mate X5 with dimensions of 11.08mm, 5.3mm, and 243g-245g; OPPO Find N3 with dimensions of 11.7mm-11.9mm, 5.8mm-6.0mm, and 239g-245g.

The Xiaomi MIX Fold 4, with dimensions of 9.47mm (folded state)/4.59mm (unfolded state) and 226g weight, ranks just below the Honor Magic V3. Vivo, Huawei, and OPPO have a folded body thickness of over 10mm, but each excels in overall performance and configuration.

Therefore, solely based on the "thinness" numerical standard, the Xiaomi MIX Fold 4 may indeed appear "thicker" than the Honor Magic V3 (0.27mm, 0.24mm), but the weight is the same at 226g. In the actual grip experience, a difference of less than 0.3mm may be practically "imperceptible".

Compared to thickness, the parameter that affects the grip feeling is the width of the body: the MIX Fold 4 and Magic V3 have body widths of 73.1mm and 74mm (folded state) respectively, with the latter being about 1cm wider (actually 0.9mm).

According to information from the supply chain and the market, one of the main reasons for the strong sales of the Xiaomi 13 series is that it is a "small screen" (6.36-inch screen) phone with a body width of 71.5mm. It can be seen that the narrower the body, the better the grip feeling.

Therefore, if the weight is the same and the difference in thickness is "imperceptible", in terms of grip feeling, the Xiaomi MIX Fold 4 outperforms the Honor Magic V3.

In terms of the main chip, the vivo X Fold 3 Pro is equipped with the second generation Snapdragon 8 (Snapdragon 8 Gen 2), while the Xiaomi MIX Fold 4 and Honor Magic V3 both use the third generation Snapdragon 8 (Snapdragon 8 Gen 3)

Main Camera Sensors are Similar

In addition to the crucial physical attribute of "thin and light" that greatly impacts the user experience, overall performance is also a key focus for flagship comparisons. Currently, the main areas of competition among major players revolve around battery life, display, body material, and imaging capabilities.

The Xiaomi MIX Fold 4 features a Leica quad-camera setup with the main camera sensor being the Light Hunter 800; additionally, it is the first to be equipped with a Leica Summilux optical lens.

The main camera lens of the Honor Magic V3 is unknown, while the main camera of the vivo X Fold3 uses a Zeiss T* coated lens.

Overall, the imaging capabilities of the Xiaomi MIX Fold 4 are quite impressive. In terms of imaging capabilities (main camera sensor + optical lens + algorithm), the Xiaomi MIX Fold 4 is not inferior to the vivo X Fold 3 Pro and should perform better than the Honor Magic V3.

Why is that?

Since the results of imaging algorithms involve software capabilities and a subjective understanding of light and shadow in the physical world, it is difficult to clearly distinguish between good and bad; understanding light and shadow also involves grasping color and tone, which are highly subjective processes and results, hence not elaborated upon.

Therefore, the actual discussion revolves around the positioning/performance of the sensor and the quality of the optical lens.

The main sensor of the Xiaomi MIX Fold 4 is the "Light Hunter 800," with a pixel output frame rate consistent with the Sony IMX 890; in terms of size, the former is 1/1.55 while the latter is 1/1.56, which are quite similar; the single pixel size completely overlaps, both being 1 micron.

A larger sensor size means capturing more light information from the natural world, resulting in higher dynamic range (HDR) in imaging and the ability to present richer details in the image.

The Light Hunter 800 has a parameter that appears very powerful: dynamic range. This mid-range sensor has a native dynamic range of up to 13.2EV, almost matching the 14EV high dynamic range of the flagship Sony mirrorless α7R5. The renowned flagship sensor Sony IMX989 also has a native dynamic range of only 10.33EV.

Dynamic range refers to the range between the brightest and darkest parts that a mobile phone camera can capture simultaneously.

In mobile photography, dynamic range significantly affects the quality of photos. For example, in high-contrast scenes in daily life, such as sunsets or sunrises, backlit shots, night scenes with bright light sources, the camera needs to have an appropriate dynamic range to clearly present details in highlights or shadows.

So, does the Light Hunter 800 surpass the Sony IMX989 in native dynamic range? In fact, it does not. In reality, the native dynamic range of the Light Hunter 800 is only about 7.32 (excluding dual native ISO fusion and dual conversion gain fusion, the technical principles of which are too complex to delve into here) Sony IMX920, with a size of 1/1.49 and an actual imaging size of 1/1.56, a single pixel size of 1.2 micrometers, was previously used in the main camera of the vivo X100. It has a dynamic range of 13.5EV, which is similar to the real dynamic range of the Light Hunter 800. As for the main camera sensor used in the Honor Magic V3, it is the IMX906, with parameters similar to the Light Hunter 800, IMX890, and IMX920, and the effects are also similar.

Which product has the best main camera lens

Since the sensor performance is similar, what about the optical lens?

The Xiaomi MIX Fold 4 became the first foldable phone in Xiaomi's history to use a Leica Summilux optical lens.

The Leica Summilux optical lens was previously used in the Xiaomi 14 series (a super popular model). Lei Jun quoted Leica's evaluation of the Xiaomi 14 on November 10, 2023, saying, "In the field of mobile imaging, the Leica Summilux lens is the most perfect so far."

According to Wall Street News, the Huawei P10 Plus in 2017 also used a Leica Summilux main camera lens with an aperture of f/1.8.

Lei Jun said, "Leica has strict grading rules for the lens series, and only apertures in the range of f/1.4-f/1.7 can be called Summilux." The aperture of the main camera optical lens of the Xiaomi MIX Fold 4 is f/1.7 (the smaller the value, the larger the aperture).

Summilux, derived from the Latin root "Summa," represents "the highest level"; "lux" represents "light," so Summilux represents Leica's large aperture lens series.

From an experiential perspective, the Leica Summilux lens mainly presents imaging characteristics of soft focus, sharp focus, and dreamy vignetting. Compared to the Leica Summicron (the optical lens used in the Xiaomi 13 series), the Leica Summilux lens is more suitable for human landscapes or portrait photography. In the Leica optical lens series, the top lens is the Noctilux lens with a maximum aperture of f/0.98.

Leica Summilux, although it is the name of a lens series, it is also a Leica lens trademark. It was applied for by Leica to the German Patent Office on May 31, 1958. That same year, Leica first used the "Summilux" trademark.

Competing with the main camera optical lens of the Xiaomi MIX Fold 4 is the Zeiss T* coated lens used in the main camera of the vivo X Fold 3 Pro.

However, the vivo X Fold 3 Pro does not specify which series of Zeiss lens is used. Zeiss lenses have multiple classifications: Tessar, Biogon, and Hologon; In addition, there is the ZA series, jointly developed by Zeiss and Sony, used for autofocus SLR lenses; it also includes the ZM/ZK/ZS/ZE series lenses, and so on.

Furthermore, although Leica does not mention its own multi-layer coating technology, it does not mean that Leica lenses do not apply this technology. Leica lenses' multi-layer coating technology is called "Leica WeCo coating", with a standard of 6 layers of coating (similar to Zeiss T* coating), which can be adjusted according to specific needs.

On the surface, the main camera lens quality of Xiaomi MIX Fold 4 seems relatively better. However, since the X60 series, vivo's main camera lens's ability to control ghosting is widely recognized, which is also part of the perceptible imaging quality experience of Zeiss T* coated lenses.

Currently, from the perspectives of "thinness" and "imaging performance", the above three folding models each have their own strengths and are all very outstanding "works".

The Honor Magic V3 in folding state is the thinnest, but the quality of the main optical lens cannot be observed; the vivo X Fold 3 Pro's main camera lens does not specify the model, but the imaging quality of Zeiss T* coating is top-notch; Xiaomi MIX Fold 4, in terms of the quality of the main optical lens, stands out among the three, and the device's "thinness" is also commendable. Therefore, the choice ultimately depends on the user's individual preferences