Samsung NX3000 ユーザーズマニュアル

Shooting Functions > 

Exposure lock

Shooting Functions > 

Exposure lock

Shooting Functions

When you cannot achieve an appropriate exposure because of a strong 
brightness contrast, lock the exposure and then capture a photo.

To lock the exposure, adjust the photo’s composition on which you want 
to calculate the exposure, and then press the Custom button. (when the 
function of the Custom button is set to AEL) (p. 139)

After locking the exposure, aim the lens where you desire, and then press 
[Shutter].