When it comes to smartphone cameras, the only number that has mattered for the past decade is how many megapixels they have. Now an innovation is arriving that makes the smartphone calculation even simpler: does it have one camera on the back or two?

就智能手机摄像头而言，过去10年唯一重要的数字是它们的像素有多少。如今，一项让智能手机的选择更简单的创新出现了：机身背面配备了一个摄像头还是两个？

A dual-lens system can bring all sorts of advantages to a smartphone that hitherto have been the preserve of standalone cameras. It can make autofocus faster and improve low-light photography. One of the pair can add extra zoom without compromising picture quality or adding bulk. The extra camera can also allow a wider angle for better landscapes and selfies. When combined with the right image-processing software it can add effects associated with expensive single lens reflex cameras, like a bokeh background or shallow depth of field, without needing to attach extra lenses.

双摄像头系统能够将此前属于独立相机的各种优势带给智能手机。它可以让自动对焦速度更快并改善低光成像效果。其中一个摄像头可在不影响画面质量或增大体积的情况下增添多倍变焦。额外的摄像头亦可提供更广的视角，以呈现更佳的风景拍摄和自拍效果。若与合适的图像处理软件结合在一起，它可以增添昂贵的单反相机可实现的效果（例如背景虚化或浅景深），而不需要安装额外的镜头。

The next iPhone is expected to come with a dual-lens camera when it is released in September but Apple will not be the first to introduce this technology. Earlier this year, LG’s G5 phone added a wide-angle lens alongside its main camera while Huawei’s flagship, the P9, comes with a Leica-branded twin-lens system that boasts image enhancements.

预计9月发布的下一代iPhone将配备一款双镜头相机，但苹果(Apple)并非第一家推出这种技术的公司。今年早些时候，LG的G5手机在主摄像头之外增加了一个广角镜头，而华为(Huawei)旗舰手机P9搭载了莱卡(Leica)品牌的双镜头系统，号称能够增强画面。

I have been testing the Huawei P9 Plus, a larger model with a 5.5-inch display, while visiting the UK — the handset has not been released in the US.

我在访问英国期间试用了华为P9 Plus，它配备了较大的5.5英寸显示屏（这款手机还没有在美国发布）。

Pros and cons

利弊

As a phone, the P9 is a handsome device with a brushed aluminium back and solid build. The fingerprint reader on its rear is fast and accurate and leaves the front face clean and smooth. I appreciated the double sim-card slots — a fantastically useful feature, still too rare in high-end smartphones, that allowed me to take calls on both my UK and US numbers without carrying two devices. However, the battery, perhaps strained by the dual-sim usage, only just made it through the day.

作为一部手机，华为P9相当帅气，拥有金属拉丝的铝合金背壳，结构坚固。机身背面的指纹识别器速度快且读取准确，使机身正面显得干净和光滑。我喜欢它的双SIM卡插槽，这一功能非常实用，在高端智能手机中也仍然太少，它让我可以在不用带两部手机的情况下，接听英国和美国号码的来电。然而，它的电池只够用一天，或许受到双SIM卡功能的拖累。

I was less of a fan of the P9 software. Huawei’s version of Android, which it calls EMUI, blings out the default apps in the same shiny gold colour scheme as the phone’s exterior, which I found tacky. That aside, the operating system looks a little too similar to Apple’s iOS, with EMUI’s square app icons and near-identical settings screen.

我不那么喜欢P9的软件。华为版的安卓(Android)系统名为EMUI，其默认应用也采用了手机外壳那种闪闪发光的金色配色方案，我认为这有点俗气。抛开这点，这款手机的操作系统看上去与苹果的iOS有点太相似了，EMUI的软件标识也采用方形设计，设置界面近乎相同。

Two lenses

双镜头

In camera technology, at least, it will be Apple that is playing catch-up with Huawei. The P9’s two lenses do not change the angle or zoom but together create a single image with greater SLR-style depth of field, where the background is blurred to make the main subject stand out. One is a regular colour camera but the other captures images in monochrome, which is better for pulling out detail and depth.

至少就摄像技术而言，将是苹果在追赶华为。P9的双摄不改变视角或焦距，但组合在一起带来类似于单反的更大景深，背景模糊而主要拍摄对象突出。一个摄像头是常规的彩色镜头，但另一个摄像头捕捉黑白影像，能够更好地捕捉细节和景深。

Taking regular photographs is no more complicated than with any other smartphone but there are lots of options. These include capture modes such as colour-saturated high dynamic range, night-shot and blemish-smoothing “beauty” mode to professional settings such as manual focus or white balance. All are instantly accessible by swiping from either edge of the screen.

一般的拍照并不比其他智能手机更复杂，但多了许多选择，包括各种拍照模式（色彩饱和的高动态范围图像、夜景，以及消除瑕疵的“美颜”模式），以及专业设置（如手动对焦或白平衡）。所有这些选项都能通过从屏幕的任一边缘滑动立即获取。

Tapping the icon that looks like a camera aperture opens one of the killer features of the dual-lens camera, its wide-aperture effects. Touch the object on which you want to focus then slide your finger up and down the screen to adjust the image to the equivalent lens aperture. Ultra-low f/0.95 will blur the background almost beyond recognition and give a very narrow focus area, while the maximum f/16 will bring the whole scene into focus. This will be familiar to people who have used SLR cameras but the design — and instant preview — is intuitive enough for those who mainly shoot with smartphones too.

轻点摄像头孔径图标，就会开启这款双镜头相机的杀手级功能之一——大光圈效果。触摸你希望对焦的图像，然后在屏幕上上下滑动手指，就能将图像调节至等效镜头光圈。超低的f/0.95将让背景模糊到若隐若现，创造出非常狭窄的对焦区域，而最高可达f/16的镜头将对整个场景对焦。这对用过单反相机的用户来说将是非常熟悉的，但其设计（以及实时预览）足够直觉，让那些主要用智能手机拍照的人也能明白。

Because this focus effect is achieved through software, the image can be tweaked after it is taken, should you decide the background is too blurred or the main subject indistinct.

因为这种对焦效果是通过软件实现的，画面可在拍摄后调整——如果你觉得背景过于模糊或者主题不清晰。

This special aperture mode works best on portraits, with the focus automatically identifying faces, and on close-range objects such as flowers. When it works, which it does best with a simple solid subject, the photo can rival one taken with an SLR. Unfortunately, however, the software is not fully reliable and sometimes smudges parts of the image at random. I noticed this particularly when my subjects had fuzzy outlines or with the curved corner of a flowerpot.

这种特殊孔径模式在拍摄肖像（对焦点自动识别人脸）和花等近距离物体方面表现最佳。它在拍摄简单的固体物件时表现最佳，可媲美单反拍照效果。然而，遗憾的是，软件并不完全可靠，有时会随机模糊局部图像。我注意到，当主题轮廓模糊或者花盆有圆弧弯角的时候尤其如此。

Verdict

结论

Like many technological firsts, the P9’s dual-lens camera is still a bit rough, or should I say fuzzy, around the edges. The special aperture effects do not work reliably enough for SLR users to leave their standalone camera at home but people accustomed to flat-looking images taken on smartphones will notice a difference.

与许多初始技术一样，P9的双镜头相机仍略嫌粗糙，或者我应该说有些模糊。特殊光圈效果还不够可靠，足以让单反用户将单反相机留在家里，但习惯于用智能手机拍摄单调图像的人们将会注意到其中的不同。

Soon, many more devices will come with dual-lens cameras. As the software improves, a meaningful change in smartphone photography is coming into focus.

很快就会有更多带有双摄的设备问世。随着软件的改进，智能手机摄影将出现有意义的改变。