Why Use Auto Exposure Lock? :: Digital Photo Secrets

Why Use Auto Exposure Lock?

by David Peterson 9 comments

Here’s a handy one for you point-and-shoot photographers. Have you ever wanted to get one part of the scene just right, but you could never get the colors to pop out? Sometimes you know more about the thing you want to photograph than your camera does. You know you want the sky to be blue, really blue, but your camera assumes you want everything to have equal importance. How can you put an end to this? Auto exposure lock, that’s how.

Photo By Tim Green

Learning how to "expose for" something

You’ve probably heard of this before. Photographers often talk about “exposing for the sky” or “exposing for the grass,” but what does it all mean? What are they really talking about?

An exposure is a complicated way of talking about a photograph. Whenever you “expose” your camera’s sensor to light, you are creating an exposure. It happens every time you press the shutter and take a picture. Light enters, hits the sensor, and an image is formed. The way light enters, how much gets in, and how it spreads across the sensor is mostly the determined by two things; the aperture and the shutter.

The photographer exposed for orange colors in the sky. Doing so made the couple completely black. This effect is known as a silhouette.
Photo By: Rajeev Nair

By controlling the aperture and the shutter, you can control exposure. That is to say, you can expose for one thing or another.

Different things require different kinds of exposure. To get a blue sky, you often need a different combination of aperture and shutter speed values than to get a lush green pasture. Whenever we talk about “exposing for” something, we mean choosing the ideal aperture and shutter speed to bring out as much color as possible from that thing.

A fun experiment you can try

I love photography experiments. That’s how I learned most of the art. So here’s one you can try, using your camera’s ordinary automatic mode.

  • On a clear day, take your camera and point it at the sky. Zoom in as much as you can and try to include the sky and nothing else. Take a picture.
  • Now, just moments after taking the first picture, point your camera more towards the ground and zoom out. Include some of the sky in the shot, but not a lot of it.
  • Compare the skies of the two photos.

A likely result of your experiment. In order to expose for the greens, and make them their greenest, you have to let in more light. That’s what makes the sky white.
Photo By: Miemo Penttinen

Here’s what’s likely to happen. The sky on the first photograph will appear very blue, and the sky on the second photograph will probably look a lot whiter. Why? Because your camera makes certain assumptions based on what it sees. It then attempts to “expose for” whatever is in its field of view. If it’s the sky, you get a nice blue sky. If it’s the green grass, you get bright green grass but the sky appears white.

Auto exposure lock gives you control over what to expose for

There are times when you will want to expose for something, change the way you frame the shot, and then take the picture. This often results in a more visually appealing composition. You could get a very blue sky by pointing your camera directly at the sky, but what’s the point if you can’t work that pretty sky it into an interesting landscape photo? That’s what auto exposure lock allows you to do.

Here’s what you need to do to use auto exposure lock:

  • Point the camera at the thing you want to expose for. That could mean pointing the camera up the sky, or zooming in to fill the frame with some bright green grass. It could even mean zooming in on your friend’s face to get the colors just right.
  • Press the auto exposure lock button. On most cameras, it’s on the back facing panel, and it’s labeled “AE-L” for auto exposure lock.
  • Reframe your picture to include everything you want to include. If you zoomed in to capture your exposure settings, zoom back out and frame the photo. It helps to pay attention to the rule of thirds and other composition guidelines.
  • Take the picture. The thing you want to highlight will appear much more colorful and detailed than every other element in the scene.

Auto exposure lock is a great primer for manual photography.

You’ll find yourself doing this all the time once you learn manual photography. Except, it won’t have a fancy name. Instead of allowing the camera to pick an aperture and shutter speed to expose for something, you’ll use a light meter, experiment, and do it yourself. Once you’ve picked which aperture, shutter speed, and ISO speed values you want to use, you’ll recompose the shot and take it. Just like above.

Now is a good time to get started with auto exposure lock. It’s a skill you’ll never forget, and it almost always comes in handy. I’m happy to help you out if you encounter any roadblocks along the way.

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  1. Kat says:

    Which metering mode should I use? Would it be different for portrait and zooming in on my friends face and for landscape? Thanks so much for this awesome article!!! It made me happy.. finally someone explaining things simply for us beginners! More of these please! :)

  2. Tammara says:

    What's up, I read your blog regularly. Your story-telling style is witty, keep it up!2

  3. Phil says:

    Just the trick I have been looking for. Once the sky is blown out to white it is not easy to make it blue. Thanks David.

  4. Riqo Irwan says:

    Very good article, easy to comprehend. Thanks a lot

  5. Brian Tite says:

    Why not compose the photo as you want it but to expose for the element you want to expose for you just have it under a selected focus point? What is the difference from autofocus/ autoexposure lock?

    • David Peterson says:

      Hi Brian,

      Some people find it quicker to use the Auto Exposure Lock, rather than having to use the camera's knobs to select the appropriate focus point.

      The AE Lock is also useful for other situations - like when you are creating a panorama or other special effect photo and you need the exposure settings to be the same for multiple shots.


      • wo hill says:

        very helpful indeed - I've been struggling to overcome the problem of 'losing' the sky in landscape pics - much appreciated.

  6. Robert Benoit says:

    I see the difference. Thanks Dave!

  7. Jeffrey says:

    Great article, thank you!!

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About David Peterson
David Peterson is the creator of Digital Photo Secrets, and the Photography Dash and loves teaching photography to fellow photographers all around the world. You can follow him on Twitter at @dphotosecrets or on Google+.