We had the opportunity to wear and review the Ref. L2.839.4.52.2, a carbon fiber version of Longines' classic diver's watch, the Longines Ultrachron. This is the brand's first time using a carbon fiber case, and it is not just a modern revival of an archive piece; it is a new milestone for the brand.
Photographs & Text by Kento Nii
[Article published on January 21, 2025]
Ultra-Chron Carbon has been reborn as a more modern product using new materials.
Longines is a prestigious Swiss watch brand founded in 1832. Since its founding, the brand has long honed its watchmaking techniques, demonstrating its pioneering spirit and contributing to the development of the aviation industry and sports timing in particular. Among the many timepieces it has produced throughout its history, the Ultra-Chron is considered a milestone in watchmaking, featuring the brand's high-frequency movements.
Longines, which has been dealing with high-frequency movements, developed and patented a timekeeping device with an accuracy of 1/10th of a second as early as 1910. Later, in 1916, they improved the accuracy of timing for sports competitions to 1/100th of a second. This technology was later applied to wristwatches, and in 1966 Longines registered the "Ultra-Chron" trademark, which was developed into a collection of watches equipped with high-frequency movements, including the Reference 7951 released the following year. The following year, in 1968, they released the "Ultra-Chron Diver" as a diver's watch.
Then, in 2022, a reissue of the Ultra-Chron Diver, the Longines Ultra-Chron, was released. The Ultra-Chron Carbon, which will be featured in this article, was released in 2025. Unlike the stainless steel model released in 2022, this model is the brand's first to use carbon for the case material. Furthermore, the entire watch is dyed completely black, giving it a new individuality.
Automatic movement (Cal. L836.6). 25 jewels. 36,000 vph. Power reserve approximately 52 hours. Titanium and carbon case (43mm diameter, 14mm thick). Water resistant to 30 bar. Price: 756,800 yen (tax included).
Combining traditional design codes with cutting-edge materials and high-frequency technology, the Ultra-Chron Carbon is a timepiece that could become Longines' next milestone.
A distinctive cushion-shaped case made of carbon
The biggest talking point about this model is the carbon fiber case, which gives it a matte black appearance, adding a modern and stoic impression to the retro cushion-shaped case design of the original 1960s model.
Furthermore, by using titanium for the bezel, crown, and case back, this model creates a contrast between different materials while pursuing lightness and a pleasant feel against the skin. As a result, despite its impressive size of 43mm in diameter and 14mm thick, the total weight listed in the catalog specifications is just 67.0g. By comparison, the stainless steel model of the same size weighs 108.1g (leather strap model). As someone who has not had much experience with watches that use carbon for the case material, the lightness and texture were extremely refreshing to me.
Another attractive feature of this watch is the layered pattern, unique to carbon fiber, seen on the case side and lugs. This pattern is created during the manufacturing process, and no two pieces are the same. Furthermore, this layered pattern harmonizes with the watch's dark two-tone color, which combines titanium and black carbon fiber.
The case back and crown are screw-down, ensuring water resistance up to 30 bar. The watch has a robust construction that evokes its roots as a diver's watch.
A face with excellent visibility and modern design
Let's take a look at the dial. It's a deep anthracite color with a matte finish that harmonizes with the case. It features three-dimensional applied indexes and simple yet powerfully shaped PVD gray hands, ensuring perfect legibility. The sapphire crystal with anti-reflective coating on both sides ensures that the dial remains visible even in sunlight, allowing for reliable reading.
The watch features a no-date design and a simple, symmetrical layout focused solely on displaying the time, giving it the feel of a tool watch. As mentioned above, the bezel is made of titanium. It is fixed and has a smooth finish on the sides. A matte aluminum insert features a scale of Arabic numerals every 10 seconds, creating a minimalist look similar to the dial.
What is particularly noteworthy about the design of this model is that it intentionally omits elements seen in the stainless steel model and the original. The rotating bezel mechanism, the one-second diving scale, and the red accents seen on the dial and hands have been eliminated, further enhancing the minimalist impression of this monochrome model.
I've been wearing it for about a week, and the sporty yet understated design with a bold black base blends seamlessly with a business jacket. The toughness of the latest materials and its versatility to suit a variety of lifestyles give it a new appeal that sets it apart from conventional Ultrachrons.
Large but comfortable to wear
As mentioned above, the titanium and carbon case weighs just 67.0g, making it comfortable to wear and obscuring the large 43mm diameter case size. I wore this watch in various situations, including desk work, and felt little stress even when wearing it for long periods of time. Naturally, this appeal will come into play even in active situations where toughness is required.
The strap is a black fabric strap that is flexible and comfortable against the skin. For my wrist, which is 16.5cm, the buckle fits snugly through the innermost hole of the strap. Therefore, if you have a wrist that is smaller than 16cm, you may need to drill an additional hole or use a shorter strap.
Cal. L836.6 produces stable high accuracy
The movement is the automatic Cal. L836.6, which has been used since the 2022 reissue model. Naturally, its greatest feature is that it has the same high-beat rate of 36000 vibrations per hour as the original. High-beat movements are less susceptible to external shocks and changes in position, allowing for more stable accuracy.
The balance spring uses single-crystal silicon, which is becoming essential for modern high-performance movements. This makes it virtually unaffected by magnetism and resistant to temperature changes. It also boasts a power reserve of approximately 52 hours, which is sufficient for a high-frequency movement, making it practically unaffected.
Furthermore, the Ultra-Chron Carbon movement has been certified as a chronometer by TIMELAB, an independent watch testing institute based in Geneva, which requires the watch to pass rigorous testing for 15 days while in its case, ensuring the accuracy of this watch.
Longines' next milestone
In this article, we review the Ultra-Chron Carbon, Longines' first watch to use carbon material and the brand's next milestone.
The use of carbon fiber is a relatively new trend in the world of watches. Originally garnering attention for its light weight and high rigidity in Formula 1 cars and the aerospace industry, its application to wristwatches, primarily sports watches, began in the 2000s. The main benefits of using carbon fiber include its incredible lightness, high strength, corrosion resistance, heat resistance, and hypoallergenic nature. However, due to the difficulty of processing and high cost, it was long limited to a few high-end models. However, in recent years, with technological advances, it has begun to be adopted by mid-range brands as well.
Given this background, Longines, known for its balance of reliability and affordability, has adopted this material for its Ultra-Chron watches, which is a part of the brand's steady evolution. Furthermore, it demonstrates a new approach to heritage, unique to Longines, which has released a wide variety of models that bring past masterpieces back to life in the modern era, drawing on its extensive archives. Rather than simply recreating past designs, the brand is reinterpreting its collections using modern materials and techniques. This timepiece could be said to embody Longines' next approach.
