大部分的紧凑型相机和所有的单反相机都有一个焦点锁定功能，通过把快门按下一半儿来实现。
Most compact cameras and all SLRs have a focus-lock capability, activated by pushing the shutter release button down halfway.
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使用反光板锁定和快门线。
Use mirror lock-up and a cable release.
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