The Sigma fp is the world's smallest and lightest full-frame mirrorless camera, according to its maker.

It is also Sigma's first mirrorless camera to support Leica's L-mount lenses since the announcement of the L-mount Alliance among Sigma, Leica and Panasonic last September. For the review, I used Sigma's L-mount 45mm f/2.8 DG DN lens with it.

The body has a footprint no bigger than that of the Apple iPhone 11, weighs a mere 370g (without battery and memory card) and has an ultra minimalist design.

It does not even have a hotshoe to mount a flash and lacks an electronic viewfinder. Instead, you can use only its fixed 3.2-inch touchscreen display, which takes up most of its rear, to compose your photos.

Without a contoured grip, the fp does not handle well even though the buttons and control dials are within easy reach. My hands feel tired after holding it for about 15 minutes.

With only a fixed display, you cannot really use it to shoot subjects from low or high angles properly. And without a dedicated mode dial, changing the shooting mode requires you to press the mode button and turn the rear wheel dial.

Sigma sells a lot of optional accessories for the fp, including a grip, a hotshoe unit and a viewfinder that mounts over the display. This is a clear indication of the fp's lean towards video.

It can shoot 4K videos in RAW video formats like CinemaDNG.

Another nod to videographers is its use of a conventional Bayer full-frame image sensor instead of Sigma's Foveon version.

Conventional Bayer image sensors have red, green and blue sensors side by side in one layer. Foveon image sensors use three layers of sensors - red, green and blue - stacked on top of one another. This allows them to better capture the colour of subjects, but at the expense of speed and is not ideal for video recording.

Nonetheless, the still image quality of the fp is good, with sharp rendition of pixels and vivid colours. But I do not recommend switching on the high dynamic range option as it will make the pictures look unnatural.

Image noise performance is stellar with little noise artefacts up to ISO 6,400. Only at ISO 12,800 do noise artefacts become more obvious, leading to some detail loss. But even at ISO 25,600, images are still usable.

The 4K video quality is top-notch - crisp with plenty of details. This is even so when shooting at ISO 25,600.

On the downside, the fp takes 1.9 seconds to power up and nearly 2.4 seconds to shut down. Most mirrorless cameras take around 2 seconds for each operation.

Using an SD card with a writing speed rated at 45MB per second, it was able to shoot 14 RAW images in 0.7 seconds before the buffer ran out.

Autofocusing (AF) is almost instantaneous under bright sunlight. In dim lighting conditions, it takes at most a second to lock onto a subject. But AF during video recording is slower. At times, it cannot even focus on a subject when I pan from one scene to another.

Also, the fp's single SD card slot might be an issue. Professional full-frame mirrorless cameras usually have two SD card slots for more storage. Battery life is also disappointing, at 280 stills on a full charge - slightly below the 300-stills norm of its competitors. But thankfully, you can recharge it via its USB-C port.