The Nikon D850 is the mid-range model in the Japanese imaging giant's full-frame DSLR camera line-up and successor to the D810, launched three years ago.

As you would expect, it comes with major improvements. For a start, it features a 45.7-megapixel full-frame CMOS image sensor (up from D810's 36.3-megapixel) with no optical low-pass filter (OLPF).

The OLPF reduces moire or wavy patterns - at the expense of image sharpness. Thus, the D800 series has always been targeted at wildlife, landscape, portrait and wedding photographers.

But now, the D850 comes with both image quality and operation speed. It uses the Expeed 5 image processor found in Nikon's flagship DSLR camera, D5. It allows a burst rate of 7 frames per sec (fps) with continuous autofocusing (AF), and up to 9fps with the optional vertical battery grip - both improvements over the D810's 5fps.

The AF system has also been upgraded to that found in D5. There are 153 AF points, which include 99 cross-type sensors. And there are 55 selectable AF points.

In addition, the D850 now supports 4K video recording as well as full high-definition slow-motion video recording of up to 120fps.

Instead of having the fixed non-touchscreen 1.2-million-dot display of its predecessor, the D850 comes with a tiltable 3.2-inch touchscreen display with double the resolution.

It features dual memory card slots that support UHS-II SD and XQD cards, compared with the slower CF card and SD card slots of its predecessor. You can save one image in RAW and a copy in JPEG, or use the second slot as extra storage.

With its weather-sealed magnesium alloy body that is resistant to dust and moisture, the D850 feels solid and robust. The ergonomic grip provides a great grasp of the camera.

The impeccable button layout of its predecessors remains largely unchanged. A front command dial sits on the grip under the shutter release, while a rear command dial is sited above the rear thumb rest for easy changing of settings. A dedicated video-recording button is beside the shutter release for you to shoot videos quickly.

There is one nice addition in the D850 - a mini joy-stick just beside the rear thumb rest. This joy-stick lets you select the AF point when you compose your picture.

The back buttons are now illuminated, so you can see which buttons to press at night. Overall, the D850's handling is superb and an absolute delight to use.

Starting up and shutting down are instantaneous, while shutter lag is almost non-existent.

Using an XQD card with a writing speed rated at 400MB per second, I shot 26 RAW images in 3.6 seconds before the buffer ran out. The speed was just as advertised.

Using the Nikon AF-S 24-120mm f/4.0 VR lens, the AF is almost instantaneous in securing a sharp focus under bright sunlight. In dim lighting conditions, it takes at most a second to lock onto a focus point. When photographing a fast-moving vehicle or running toddler, the D850 was able to keep pace and consistently delivered asharp focus.

Image quality ranged from excellent to jaw-dropping, with sharp image rendition and amazingly rich details in the photos I shot. With portraits, I could differentiate the different strands of hair of my subjects. Zooming into a landscape photo yielded details that are distinct and sharp. Guess this is what a 45.7-megapixel image sensor is able to achieve.

Image noise performance is equally stellar. Images look spotless and without noise artefacts up to ISO 1,600. Even at ISO 3,200, I could hardly see any image noise. Only at ISO 6,400 did some chromatic noise artefacts appear, along with slight detail loss.

Both 4K and full high-definition videos look crisp with plenty of details. While its predecessor often has to hunt for a focus, the D850 is able to lock onto a focus within 2sec when panned to a new scene.

The D850's battery life is quite superb, registering more than 1,800 still images on a full charge - 600 more than the D810. It still pales in comparison with the D5's 3,800-still-image battery life, though.

• Verdict: With its swift operation, deadeye-accurate autofocusing and excellent image quality, the Nikon D850 is probably the most all-rounded full-frame DSLR camera I have tested - finally, something worthy of Nikon's centennial year.