Exposure Lock

Exposure Lock (AE-L on Nikon and usually the star button for Canon) can be used to great effect in conjunction with spot metering. It allows you to lock the exposure on a certain point, and then you can recompose the photo while maintaining the locked exposure.

Exposure lock only has an effect on the photo in A, S, TV and P mode.

Usually your camera constantly reads the light from the meter and adjusts the exposure accordingly. If you are A mode you will notice that the camera adjusts the shutter speed depending on how bright or dark the scene it. If you point your camera at a different part of the room that is brighter or darker you will see the shutter speed change.

When you press the exposure lock button your camera locks the exposure by fixing the current aperture, shutter speed and ISO until you take the photo. This is useful when you want to correctly expose a certain element in your photo that is not in the middle of the scene. To do this put your camera in spot metering mode, then press the exposure lock button when the part of the photo you want to expose correctly is in the middle of the photo. This will lock the exposure and you can recompose the shot.

Here’s an example where the photographer used spot metering and exposure lock. By putting the camera in spot metering mode, then pressing exposure lock when an orange part of the sea was in the middle of the viewfinder, the photographer could then re-compose the image and take it at the desired exposure.