You'll need to lock the focus if you have an auto-focus camera because most of them focus on whatever is in the center of the viewfinder. Try it yourself.

如果您使用的是自动对焦相机，您需要先锁定焦点，这是因为大多数相机将焦点对准取景器中心的物体。

youdao

Can also sent auto-exposure and auto-focus lock.

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Also the camera's hi-speed auto focus can lock onto subject in as little as 0.1 seconds, letting users grab the most fleeting photo moments with ease.

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