Sony's Alpha NEX-5 bridges the gap between compact camera and digital SLR with some high-performance features  - UPDATED 18 NOV 2010

There’s a wholly new category of high-spec digital cameras appearing that’s really mixing up the photography market. Problem is, no-one’s really quite sure what to call them.

First to market was Olympus with its digital E-P1 PEN model, which promoted the ‘four-thirds’ name – in reality, a reference to the sensor size which is the same as an old 4/3in video camera tube.

Also known as a mirrorless camera - or compact system camera (CSC) by review sample supplier Jessops - the key point here is upmarket picture quality and manual versatility to rival professional DSLR cameras. But crucially, much smaller and lighter.

Even the lenses tend to be more compact, further encouraging you to take the camera to places that you wouldn’t want to lug an SLR.

And the all-important light sensor is large in size, when compared to the 1/2.5in types found in most compact digital cameras. At 17.3 x 13mm, the four-thirds sensor is almost ten times the area, which helps enormously with reducing grain and noise, and improving low-light sensitivity.

Besides four-thirds though, another popular sensor size – and one that’s larger again – is APS-C, named after ‘advanced sensor size - classic’. It’s often sized at around 23 x 15mm and it’s the type of sensor seen in most digital SLR cameras now.

It’s also the sensor type chosen by Sony for the Sony NEX-5 – its lightweight contender in this new in-betweener category.

The Sony NEX-5 has a light magnesium alloy body weighing just 299g, or 485g with the 18–55mm lens.

With that 18–55mm lens attached, it’s not quite as pocketable as a compact, but the Sony NEX-5 nevertheless remains a very portable camera. Optionally available is a more modest 16mm f2.8 pancake lens, as well as an 11x-zoom 18–200mm f3.5–6.3 lens.

There’s no separate viewfinder, so you must use the rear LCD display to frame your photos. That's fine most of the time, but srong daylight will have you shielding the display so you can see what you're shooting.

The same display also provides a graphical interface to control most of the camera’s functions. This includes the all-important mode dial - the PASM switch (Program, Aperture priority, Shutter priority, Manual) - which must also be negotiated though a virtual picture on the screen, via a real multi-function dial on the camera's back.

Build quality of this Sony is fabulous, those real metal alloys seamlessly assembled. Taking a picture is a joy, thanks to good balance in the hand and a reassuring whirr-click as the shutter is released. There’s little shutter lag in shooting either, making it easy to capture what you see, as you see it.

Video mode works well, preserving your cinematography in high-definition 1920x1080 resolution, although sadly in interlaced 1080i format AVCHD rather than 1080p progressive scan. Sound recording is stereo, from two small mics on the top of the body.

Still images are shot as either JPEG or RAW, or both. The miniumum ISO of 200 may seem high, but we found pictures to be very smooth and noiseless. Even at elevated ISO settings of 1600 for low-light use, the Sony NEX-5 took clean images. You can ramp up to ISO 12,800, by which point you will see plenty of noise of course.

We also enjoyed the auto Sweep Panorama stitch mode, which created well-joined and very wide landscape shots, even knitting together seascapes quite convincingly.

Battery life is very good, able to shoot several hundred shots in a day and still have around one-third power remaining. And Sony has relented on its proprietary memory-card obstinacy, with the Sony NEX-5 supporting both SD/SDHC cards and Sony's own Memory Sticks.

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