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A closer look at the Sony Xperia XZ2 Premium’s dual cameras in low-light

By Alvin Soon - 18 Aug 2018,1:30pm

Ultra-high sensitivity is more than just high ISO

Note: This article was first published on 8th August 2018.

Sony's first phone with dual rear cameras

It’s a crowded world that the Sony Xperia XZ2 Premium comes into. Not only does its camera have to do better than last year’s XZ Premium and this year’s Xperia XZ2, it has to contend with the likes of Apple’s iPhone X, Samsung’s Galaxy S9, and Huawei’s P20 Pro.

The XZ2 Premium steps up to the plate with a dual rear camera system. It’s the first time Sony is using a dual camera system on its smartphones. It’s not a wide-angle and telephoto combination like on the iPhone X. The XZ2 Premium goes for a color and mono combination like on the Huawei P10:- 

  • Main rear camera: 19MP, 1/2.3-inch color sensor with a 25mm f/1.8 lens
  • Secondary rear camera: 12MP, 1/2.3-inch mono sensor with a f/1.6 lens.

In theory, having two sensors combine images taken at the same instance will produce a single image that’s better. This is usually because the mono sensor doesn’t have the color filter array that can blur details, so a dual system can add those details back in post after the scene has been captured.

Sony is championing extreme low-light photography as one of the XZ2 Premium’s highlights. The dual camera system can take photos at up to ISO 51,200 for photos, and ISO 12,800 for videos

(The XZ2 Premium doesn’t ship with optical image stabilization, which would have been a boost for low-light photography. Instead, it relies on electronic image stabilization.)

Since low-light photography is one of its key features, I decided to take the XZ2 Premium for a walk in the dark. Here’s what I discovered.

 

Ultra-high sensitivity is more than just high ISO

Without UHS (left), and with UHS turned on (right).

The XZ2 Premium’s high sensitivity works to its benefit in low-light. The high ISO opens up dark areas that are otherwise black patches. It gives you a fighting chance at capturing something when there’s little light.

It appears that ‘ultra high-sensitivity’ (UHS) is not just a high ISO setting. With UHS turned on, the XZ2 Premium captures more detail in an image than from boosting the ISO in Manual mode. I imagine that’s the dual camera system doing its work.

You might have to squint to see it, but the UHS image (right) has more detail in the rock and granite than the non-UHS image (left). According to the EXIF data, both images were shot at the same settings, so it’s likely the dual camera system that’s making the difference.

But while it puts back more detail, UHS has its limits. For example, it doesn’t bracket exposures to create a single HDR image. At least, not from what I can see. When you shoot a scene that has high contrast between shadow and highlights, UHS doesn’t make much of a difference.

There’s not much difference in this scene even with UHS turned on (right). The camera still tries to expose evenly for the light, which means shadows are lost. It’s also a clue that the XZ2 Premium isn’t doing any kind of HDR-like processing.

In this case, UHS is behaving as you’d expect high ISO to behave. It follows the camera’s metering to produce as even an exposure as it can. This usually means blown highlights and damp shadows in high contrast lighting. It’s the same way your DSLR behaves if you turn it to Program Mode and manually adjust the ISO.

By the way, you should know that UHS can’t be manually activated in Superior Auto mode, the XZ2 Premium will decide when it should turn it on. You can manually control it in Manual mode. And the XZ2 Premium says UHS only works with subjects at least five meters away, although I’ve had it work at closer distances.

UHS does best in scenes that are evenly dark, not scenes that have bright and dark contrasts. At ISO 3,200, this scene is a complete blank (left), which is what it looked like in real life. With UHS turned on, the camera shoots at ISO 51,200 and captures more than what the eye can see.

Here’s a closer look at the UHS image shot at ISO 51,200. It’s remarkably clean for such a high ISO shot, especially since it’s coming out of a smartphone.

You should also know that the highest ISO 51,200 setting is only available in certain resolutions (13MP and 12MP at 16:9, 17MP and 12MP at 4:3). This usually works out, as these are the highest resolutions in Superior Auto mode. Unless you want to shoot in Manual Mode at the maximum resolution of 19MP at 4:3. That resolution, and others in Manual Mode like 17MP at 16:9, only go up to ISO 12,800.

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