幕后：Google的像素摄像机根本不是试图成为摄像机

If you’re searching for a smartphone with a good camera, there’s no doubt you’ve seen Google’s Pixel series on a list of recommendations. Year over year, Google has figured out how to make a camera that delivers great results every single time. From the pixel-peeping tech blogger to the everyday consumer, it’s hard to find a single person that doesn’t love the Pixel’s cameras.

除了Google并没有试图制作相机。它试图使魔术变得魔术。

I recently had the opportunity to sit down with Marc Levoy and Isaac Reynolds – the core minds behind the Pixel series’ frustratingly-good camera system. We had long conversations about the new features in the像素4相机，从其改进夜视to its WYSIWYG (What You See Is What You Get) real-time HDR+ viewfinder. There was a lot of technical talk about how Google is enabling these features, but one thing was made crystal clear by the end. Google’s Pixel camera isn’t about trying to be a camera at all.

“Our core philosophy is building a camera that does magic, which is that combination of simplicity and image quality,” explained Reynolds, “So Night Sight is still there, default HDR+ is still there. All the processing that goes on under the hood to get a great photo from the default mode is still there. And we’ve also actually done a lot more simplification.”

默认模式。简化。魔法。这些是Google用作Pixel相机核心理念的一部分。在Levoy和Reynold的脑海中，捕捉时刻不需要与模式表盘和设置菜单有关。Google并没有试图在手机中构建摄像头，而是试图通过传统手段或其他方式构建使始终如一的出色图像构建的东西。

你所看到的就是你得到的

One of the Pixel 4’s new features is the WYSIWYG viewfinder, meaning you’ll see the results of HDR+ before you even take the shot. This might seem like a minor feature, but it enables some things that just aren’t possible in non-computationally-driven cameras.

Wysiwyg取景器的目标是尽可能减少用户交互。通过在打开相机时正确显示所得图像，您将知道您是否立即获得均匀的曝光，并且可以专注于钉子。

“如果我们看到用户点击了，我们就会知道相机从一开始就不会给他们他们想要的东西。”继续雷诺兹：“对我来说，抽头是我们要改善的失败案例。”

传统的摄像头系统非常糟糕，无法直接从相机中取出图像。您可以揭露高光，以后再抬起阴影，也可以暴露于阴影，但要吹出亮点。多亏了技术，我们可以同时做，这是计算摄影真正开始使这种魔术实现的地方。

“Having a WYSIWYG viewfinder now means that we can rethink how you control exposure on the camera if you’d like to.” says Levoy, “So if you do tap, whereas before you would get an exposure compensation slider, you now get two sliders. We call this feature Dual Exposure Control. And it could be highlights and shadows. It could be brightness and dynamic range. There are lots of ways you could do those two variables. We’ve set it up to do brightness and shadows. And that gives you a kind of control that no one has ever had on a camera before.”

Levoy is right. Dual Exposure Control is something that can only be produced through computational imaging. As a baseline, the image will be even, with preserved highlights and visible shadows. But if you want, you have the power to individually adjust highlights and shadows, before you even take the photo. That’s something you previously could only do in photo editing software, after you take the photo.

Levoy’s team is trying to see past the limitations of the traditional camera by focusing its efforts on the limitations traditional cameras have. While most manufacturers are introducing Pro modes to give you control of aperture, shutter speed, and ISO, Google is trying to automatically make a better image than you could, even if you had those knobs just right.

Kill it with learning

So what other ways can computational imaging out-pace traditional camera techniques? This year, Levoy’s team is tackling low-light.

Pixel 4将基于学习的白平衡引入其相机系统。即使在极不良的光线下，此功能也可以不断改善图像中的颜色。Google专门针对弱光和黄色的灯，并用使用的钠蒸气灯作为它试图修复的事情的一个例子，但旨在每次获得完美的白平衡。

钠蒸气灯是一种燃气灯，由于其极狭窄的波长为589nm至589.3nm，对受试者产生了几乎单色的影响。它们之所以使用，是因为它们是高效的光源，因此您经常在路灯或其他需要持续很长时间的灯中看到它。这是获得准确白平衡的最困难情况之一，因此Google的软件修复程序确实令人印象深刻。

莱沃伊说：“在钠蒸气光的情况下，[不良光]将是黄色的，我们将尝试中和那种不良的照明。”“ [不正确的白平衡]在较低的光线下发生了很多事情。如果您走进迪斯科舞厅并且有红色的霓虹灯，它将保留它，但会试图中和一些不利区域的照明。”

Learning-based white balance was already present in Google’s Night Sight mode, which is why its final image had much better color than something like auto mode on the华为P30 Pro。该系统根据对其认为具有良好平衡的设备拍摄的图像进行学习，并使用学到的数据在光线不佳的情况下产生更多的颜色精确图像。这是传统的相机系统无法做到的。相机发票后，自动白平衡为自动白平衡。在像素上，随着时间的流逝，它总是在努力变得更好。

基于学习的白平衡使出色的低光图像变得更加容易，但是Levoy希望使用计算机简化曾经难以置信的成像形式 - 天文学。

看星星

Levoy calls this new capability “HDR+ on steroids”. Where standard HDR+ takes a burst of 10-15 short exposures and aligns and averages them to get sharp imagery with low noise, this new mode takes up to 15 sets of 16-second exposures, to create a 4-minute exposure. The system then aligns the images (since stars move over time) and adjusts the appropriate settings while reducing noise with pixel averages to create some astounding images.

莱沃伊（Levoy）向我展示了他的团队以银河系的方式拍摄的照片，我的下巴实际上掉了。虽然可以在传统的摄像头系统上进行长时间的曝光，但通常需要额外的设备来随着时间的推移将相机转动。有了夜视，您可以简单地将手机靠在岩石上，撞到快门，然后将其剩下。

Perhaps the smartest part of this newAstro Night Sight modeis that it isn’t a separate mode at all. It all happens with the Night Sight button. HDR+ already uses the gyroscope to detect motion and align bursts of images, and Night Sight will now detect how long it can feasibly take an image depending on how steady the device is when you hit the shutter button, up to four minutes. It will also detect skies using a method called Semantic Segmentation, which allows the system to treat certain areas of the image differently for the best result.

雷诺兹说：“我们希望任何人都可以轻松使用任何东西，因此，每当我们在产品中找到不需要在那里的东西时，我们都可以从您身上承担责任并为您解决。”

That statement really boils down what Google is trying to do with Pixel’s camera. Instead of looking to how they can make it operate like a camera, Google is trying to solve issues you didn’t even know existed, and present it in the simplest possible form.

Of course, there are merits to both sides. Some people might想手机摄像机像相机一样操作，并带有手动控件和拨号。他们可能想要更大的传感器和专业模式。但是，尽管其他ODM几乎只专注于硬件，但Google却朝着完全不同的方向寻找。

It’s looking to make magic.

想了解有关计算摄影的更多信息吗？查看上面的视频，以了解该字段将如何改变我们制作图像的方式。