AE Lock stands for Automatic Exposure Lock, usually a button on the camera body of advanced cameras such as Digital Single Lens Reflex (DSLR) models.

When the shutter-button is half-depressed the camera takes an exposure reading (and focusses on the subject). At this stage the photograph has not been taken, but pressing the AEL button will lock the exposure reading. Its use is for more specialised applications (for example spot-metering, where the exposure needs to be locked.

The way the AEL button functions can be varied by accessing its control in the camera menu. Usually when the button is released the lock is removed, but depending on the camera model, it is also possible to maintain the lock until the photograph is taken.

The use of the AEL button is discussed further in spot-metering.