AE lock, or auto exposure lock, is a function that’s not talked about much. I think this is because most photography educators, myself included, recommend learning how to use manual mode. In which case you won’t need AE lock. BUT that doesn’t mean that the other modes aren’t good, useful and have their place.
When to use auto exposure lock
You’ll find these auto exposure lock tips helpful if you photograph in:
- Program mode
- Aperture priority mode
- Shutter priority mode
It’s not so great if you prefer to use back button focusing, unless you assign the AE lock function to another button using custom settings. The reason being is that you don’t have enough thumbs to push all the buttons.
Also, if you’re used to using single point autofocus and moving the focal point around rather than metering and recomposing a shot, you won’t need auto exposure lock.
Further reading: Why Back Button Focus is your BFF, and how to use it
With that said, let’s explore auto exposure lock. We’ll look at:
- What is auto exposure lock
- The benefits of using AE lock
- How and when to use AE lock
What is auto exposure lock?
On the back of your camera you’ll see a button labelled AE-L. That’s your auto exposure lock button and it does what it says on the tin (button).
When you depress and hold the auto exposure lock button it locks the exposure.
If you then move the camera to recompose, while still holding down the auto exposure lock button, the exposure settings won’t change, regardless of where you’re pointing your camera.
Why use auto exposure lock?
Let’s say you’re photographing a couple, but you want them off to the side of the scene, not smack bang in the middle of the photo.
You’ll want to ensure that the photograph is correctly exposed for the couple. So you need to be able to expose for them, but then recompose the shot without the exposure changing when you recompose.
How to use auto exposure lock
Using the example above:
- Position the focal point on the couple
- Meter off the couple to get your exposure reading
- Push and hold down the AE lock button
- Recompose and push the shutter button to take the shot
If you continue to hold down the auto exposure lock button you can continue taking photos at that exposure for as long as you hold down the button. So the couple could move, you could move, you could reframe the image, but the exposure settings would remain the same.
If you find spot metering and single point autofocus confusing, here’s a handy cheat sheet you can download.
Also, here’s more information: Clearing up the confusion between spot metering and single point autofocus
Why not just reposition the focal point to meter?
Let’s use a headshot as an example.
When photographing people, we focus on the eye. However, exposure should be set for the skin. If you simply move the focal point over the eye and take an exposure reading based off that (using spot metering), it will be wrong.
For a well exposed, sharp headshot photo, follow these steps:
- Meter for correctly exposed skin by positioning the focus point on their cheek
- Depress and hold the auto exposure lock button to lock in exposure
- Recompose and position the focus point over their eye
- Press the shutter button half way to focus and depress full to take the shot
You see why this wouldn’t work if you use back button focus with the shutter button for shutter release only? You need to be able to use the shutter button to focus with this technique, because your thumb will be busy holding down the auto exposure lock button.
Is AE lock only for spot metering?
No. You can also use it in the same way with partial or center weighted exposure metering. In this instance you would be exposing for a larger area than with spot metering. For example photographing a dog running on the beach.
However, there’s no point using auto exposure lock with matrix metering / evaluative metering, because your camera is exposing for the whole scene anyway.
Further reading on metering: Understanding how exposure metering works – controlling exposure part 2
Why not just use manual mode?
Not every photographer wants to use manual mode. Also, some situations are too fast moving to use manual mode.
I don’t advise using program mode, as you leave too much up to the camera to decide and it doesn’t know enough about what you’re photographing. Too much responsibility for your camera and it can make the wrong choices.
However, sometimes it is better to use aperture priority or shutter priority over manual mode. They are much faster to use than manual mode when there’s a lot going on and you don’t have time to change your aperture and shutter speed settings quickly.
Some examples for aperture priority mode or shutter priority mode:
- Confetti toss at a wedding
- Kids playing
- Concert with flashing or moving lights
Further reading: What are the best shooting modes to use and why?
Final words on auto exposure lock
There are so many ways to arrive at the end result of a sharp, well exposed photograph. Different situations call for different techniques. Knowing all the methods prepares you for all situations.
Auto exposure lock is just one method of achieving a well exposed photo and is well worth practicing for when you might need it.
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