Explanation: This button can „freeze“ the exposure and / or focus at the moment you push it and as long as you hold the button pressed. An indicator „AE-L“ will be displayed in the viewfinder as long as the exposure metering is locked, for the autofocus lock there is no display to confirm it.
This does not work in the camera modes AUTO and .
AE-L is the abbreviation for „auto exposure lock“, AF-L for „auto focus lock“
What exactly this button does is defined in the custom setting menu f2 assign AE-L/AF-L button. If you have not changed it it will lock both exposure metering and autofocus.
The button has a specific function if you have just stopped the playback of a movie with the arrow pointing down on the multi selector: Then you can enter a menu to cut the movie and to save the current frame as an image on its own.
Recommendation: The auto exposure lock is simple and effective if you have a subject with high contrasts and want to get the exposure right for a certain area.
Be careful: Because in the default settings the AE-L/AF-L button will also lock the focus you need to either focus correctly beforehand or change the custom setting menu f2 Assign AE-L/AF-L button to lock exposure only.