Panasonic DMC-G1K Operating Instructions Manual page 75

Note
If you set [AF/AE LOCK HOLD] in the [CUSTOM MENU] menu to [ON], you can fix the focus
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and the exposure even if you release the [AF/AE LOCK] button after pressing it. (P106)
AE Lock only is effective when taking pictures with manual focus.
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The exposure is set, even if the brightness of the subject changes.
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The subject can be focused again by pressing the shutter button halfway even when AE is
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locked.
Programme shift can be set even when AE is locked.
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Advanced (Recording pictures)
VQT1U50
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