AE lock (AE-L) is a camera feature, usually activated via a button or lever, that locks the automatically measured exposure reading into memory while you recompose your shot. This is particularly useful in challenging lighting situations, such as backlit subjects, where you want to measure light on the subject rather than the background. For example, you can point the camera at the subject, lock the exposure, recompose the frame, and then take the photo to ensure correct brightness. AE-L is also helpful for landscapes with bright skies-pointing the camera down to meter, locking the exposure, and then shooting allows you to control exposure accurately. Photographers use AE lock to bias exposure toward a specific area or maintain consistent results in variable lighting conditions.