自动对焦模式与af区域模式

Modern technology has made photography a lot more accessible. In the early days, photographers had to painstakingly focus their lens by hand before they took a photo. If they missed focus, the image (and the expensive film they were using) would go to waste. Now, almost all cameras, from your smartphone to a high-end DSLR, use autofocus to make it easier to get sharp shots.

现代技术使摄影变得更加容易。 在早期，摄影师在拍摄照片之前必须辛苦地用手对准镜头。 如果他们错过焦点，图像(以及他们使用的昂贵胶片)将浪费。 现在，从智能手机到高端数码单反相机，几乎所有相机都使用自动对焦，使拍摄清晰照片变得更加容易。

Unfortunately, when the camera does everything in the background, many photographers don’t really understand what’s going on. They just point their camera, push the shutter button and hope that the camera will get the shot. If you want to really take control of your images, you need to know a bit more about autofocus and how to use it.

不幸的是，当相机在后台执行所有操作时，许多摄影师并不真正了解正在发生的事情。 他们只是对准相机，按下快门按钮，并希望相机能够拍摄出来。 如果您想真正控制图像，则需要进一步了解自动对焦及其使用方法。

自动对焦的工作原理 (How Autofocus Works)

Most modern cameras use passive autofocus instead of active autofocus. Rather than using a laser or infrared beam to measure the distance to the subject (active autofocus), passive autofocus uses a phase detection, contrast sensors, or often a mix of both. On a smartphone, the image sensor might double as the autofocus sensor. On a DSLR, there will normally be specific autofocus sensors embedded in the image sensor.

大多数现代相机都使用被动自动对焦而不是主动自动对焦。 被动式自动对焦不是使用激光或红外线束来测量到被摄对象的距离(主动式自动对焦)，而是使用相位检测，对比度传感器或两者的混合。 在智能手机上，图像传感器可能是自动对焦传感器的两倍。 在数码单反相机上，通常会在图像传感器中嵌入特定的自动对焦传感器。

Although phase detection and contrast sensors use different methods, they both basically rely on areas with edges and contrast. The camera calculates what adjustments it needs to make to the focus of the lens so that the edges and areas of contrast are as sharp as possible. The logic is that when edges are sharp, they’re in focus. There’s a bit more going on when it comes to how the camera decides where the subject is in the frame, but we’ll address that in a moment.

尽管相位检测和对比度传感器使用不同的方法，但它们基本上都依赖于具有边缘和对比度的区域。 相机会计算需要对镜头焦点进行的调整，以使边缘和对比度区域尽可能清晰。 逻辑是，当边缘很锐利时，它们就会成为焦点。 关于相机如何确定拍摄对象在画面中的位置，还有很多事情要做，但是我们稍后会解决。

These autofocus systems work great, in most cases. They fall down in low light, however, or when you are trying to focus on something that has no edges or contrast, like a flat blue sky or white wall. Your camera will normally still work, but in the worst cases, it will just take it a lot longer to find focus.

这些自动对焦系统在大多数情况下都可以正常工作。 但是，它们会在光线不足的情况下掉下来，或者当您试图聚焦在没有边缘或对比度的物体上时，例如平坦的蓝天或白墙。 您的相机通常仍可以工作，但在最坏的情况下，它只会花很长时间才能找到焦点。

自动对焦点 (Autofocus Points)

When you look through the viewfinder of a DSLR, you see a grid of dots or squares. These are autofocus points. Entry level cameras might only have a few autofocus points while professional cameras can have 60 or 80.

当您通过DSLR的取景器查看时，会看到点或正方形的网格。 这些是自动对焦点。 入门级相机可能只有几个自动对焦点，而专业相机可能只有60个或80个。

By default, most cameras will automatically select which autofocus point (or points) to use. The algorithms they use tend to assume that the subject of the image is somewhere near the center of the frame. It’s not a bad system, but it doesn’t give you a huge amount of control. If your subject is standing to the side, you might miss focus.

默认情况下，大多数相机会自动选择要使用的一个或多个自动对焦点。 他们使用的算法倾向于假定图像的主题位于帧中心附近。 这不是一个糟糕的系统，但它并不能给您带来大量的控制权。 如果您的主体站在一边，您可能会错过焦点。

To get better photos, you need to take charge. With almost all cameras, you’re able to specify an autofocus point, or group of autofocus points, you want it to use. While there are too many variations to go into here, generally there will be a button, or combination of buttons, you press that swap between different autofocus point options. On smartphones or mirrorless cameras, you can often select an autofocus area just by tapping where you want the camera to focus on the touch screen.

为了获得更好的照片，您需要负责。 在几乎所有相机上，您都可以指定要使用的自动对焦点或一组自动对焦点。 尽管此处有太多变化，但通常会有一个按钮或按钮组合，您可以按此按钮在不同的自动对焦点选项之间进行交换。 在智能手机或无反光镜相机上，您通常可以仅通过点击要相机聚焦在触摸屏上的位置来选择自动对焦区域。

Check your camera’s manual to find out more.

查看相机的手册以了解更多信息。

不同的模式 (The Different Modes)

As well as selecting an autofocus point, you can also select an autofocus mode. These tell your camera what to do when it’s looking for focus.

除了选择自动聚焦点之外，您还可以选择自动聚焦模式。 这些告诉您的相机在寻找焦点时该怎么做。

单次自动对焦模式 (Single Autofocus Mode)

One-shot AF (Canon) and AF-S (Nikon) modes are for static scenes like landscapes. Once your camera has found focus, it stays locked. If something moves in the scene—say, a bird flies through—it will be ignored. It’s the simplest to use and almost never misses focus.

单次AF(佳能)和AF-S(尼康)模式适用于风景等静态场景。 相机找到焦点后，它将保持锁定状态。 如果场景中有东西移动(例如，一只鸟飞过)，它将被忽略。 这是最简单的使用方法，几乎​​不会遗漏任何焦点。

连续自动对焦 (Continuous Autofocus)

AI Servo (Canon) and AF-C (Nikon) modes are for scenes with a lot of motion. Your camera will never stop adjusting focus. If you’re trying to track a football player as they run, it’s the mode to use. As the subject moves through the frame, the focus will constantly get adjusted. The issue with this is that if you’re trying to focus on a relatively still scene, your camera might jump the focus around.

AI伺服(佳能)和AF-C(尼康)模式适用于运动频繁的场景。 您的相机将永远不会停止调整焦点。 如果您要在足球运动员跑动时对其进行跟踪，则可以使用这种模式。 当拍摄对象在画面中移动时，焦点将不断调整。 这样做的问题是，如果您试图聚焦在相对静止的场景上，则相机可能会跳焦。

混合自动对焦 (Hybrid Autofocus)

AI Focus (Canon) and AF-A (Nikon) modes are a hybrid of single and continuous autofocus. When the scene remains static, the autofocus will lock. If something moves, it’ll adjust until it finds focus again. If you’re not sure what autofocus mode to use, it’s a safe and flexible bet.

AI对焦(佳能)和AF-A(尼康)模式是单次和连续自动对焦的混合。 当场景保持静止时，自动对焦将锁定。 如果有什么动作，它将进行调整，直到再次找到焦点。 如果您不确定要使用哪种自动对焦模式，那将是一个安全而灵活的选择。

Those are the basics of autofocus. More advanced cameras will have more advanced options buried in their settings. For example, the Canon 1D, 5D, and 7D lines let you configure exactly how continuous autofocus tracks subjects.

这些是自动对焦的基础。 更高级的相机将在其设置中包含更多高级选项。 例如，佳能1D，5D和7D线可让您精确配置连续自动对焦跟踪对象的方式。

It’s worth taking the time to read your camera’s instruction manual and find out how to select autofocus points and modes; it will make getting accurate focus (and more importantly, sharp images) a lot easier.

值得花时间阅读相机的使用说明书，并了解如何选择自动对焦点和模式。 这将使获得准确的焦点(更重要的是获得清晰的图像)变得容易得多。

翻译自: https://www.howtogeek.com/297685/what-is-autofocus-and-what-do-the-different-modes-mean/

自动对焦模式与af区域模式