A Beginner’s Guide to Using AE Lock

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A Beginner’s Guide to Using AE Lock

ae lockIn my last post about metering, you may have noticed that I made a quick reference to “AE Lock.”  You may be unfamiliar with what AE Lock is or what it does.  Never fear, I am here to tell you all about it!

What is AE lock?

AE lock (autoexposure lock), simply put, is a function on DSLRs that locks the exposure for a set amount of time so that exposure settings won’t be changed.

That’s nice.  But when and why would I use it?

Good question!  In my last post about metering, I talked about spot metering.  If you are using spot metering (especially with a camera brand where spot metering does not follow the focus point and is, instead, in the center of the viewfinder, causing you to meter and then recompose), and are shooting in manual, you would meter, dial in your settings, and then recompose, focus, and shoot.  But you may not be shooting in manual.  You may be using one of the other modes, such as Aperture Priority, Shutter Priority, or Program.  In these modes, you still have the ability to spot meter.  However, if you spot meter off a subject, especially a backlit one, and then recompose, you will notice your settings will change.  This is because the camera is metering in real time, and is now metering from where you recomposed to, rather than from your original intended metering point.  This will result in photos where the subject is underexposed, sometimes drastically.  So how do you get around this?  How do you keep your exposure set at what you originally metered from?  This is where AE Lock comes in!  Using the AE Lock function on your camera will allow you to lock in settings from your original meter reading, and those settings will not change when you recompose your photo.

Below are two example photos I took specifically for this post to demonstrate the principle.  Both were taken in aperture priority mode at f/3.5, and both are straight out of the camera.


I did not use AE lock in the previous photo.  Notice how my lovely assistant is somewhat underexposed.  This is because when I recomposed my photo, the camera was metering from the brighter area of the dock in the background, rather than on my subject.


I did use AE lock on the previous photo.  I metered off my subject’s face, just like in the first photo, but then used AE Lock when I recomposed and took the shot.  Notice my lovely assistant is now better exposed.  I did not use any exposure compensation on this photo; I normally might use + 1/3-2/3 (as you get to know your camera, you will learn these little things) but I wanted to use shots with no adjustments for this post.  Also notice that now, the background is brighter and there are some blown out areas with lost detail in the sky.  This is a trade off when shooting backlit subjects, whether you are using AE Lock in a creative mode or are shooting manual.

How to use AE Lock?

The AE Lock function is generally accessed via a small button on the top right of the back of your camera.  The location varies slightly by camera brands and there are even differences between different camera models made by the same brand, so consult your manual to find out exactly what button you should use and determine if there is any custom set-up needed.  Across all brands, the process for using AE Lock is the same:  meter off desired subject, then press the AE-Lock button to lock in those settings for a short period of time (usually around five seconds), giving you time to recompose and shoot.  Your camera may also give you the ability to hold down the AE Lock button, thus locking your exposure until you release the button.  Check your manual for this as well.

Can I only use AE Lock when I spot meter?  What if my camera doesn’t have spot metering?  Or what if I have a camera brand where spot metering follows the focus point, do I still need AE Lock?

You can use AE Lock in whatever metering mode you would like (though in most cameras, in evaluative/matrix metering mode, the exposure is locked when you half-press the shutter button).  You can use it in partial metering, center-weighted…really at any time where you want to lock the metering on any specific area and you do not want it to change even if you recompose the shot.  I would still recommend using AE Lock on camera brands where spot metering follows the focus point.  Why?  Because if you are photographing a portrait, where are you going to focus?  The eye.  However, it’s quite likely that your subject’s eye is actually darker than their skin, which you want properly exposed, and if you used a meter reading from the eye, you will most likely end up with an underexposed photo.  Metering from the skin, using AE Lock, and then recomposing and focusing on an eye would be the best way to get proper exposure even with these cameras.

Using AE Lock takes just a little bit of practice, but once you understand what it is and how to use it, you can achieve the exposure you want in your photos.

Amy Short is the owner of Amy Kristin Photography, a portrait and maternity photography business based in Wakefield, RI.  She takes her cameras with her everywhere, even if she’s not doing a shoot.  She loves to make new Facebook fans, so be sure to check her out there too!

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  1. November 7, 2013 at 1:41 pm —

    Hi Bailey, if your camera has just one button that can be assigned to both AE-Lock and autofocus, you would need to check your camera manual to determine if there is a way to use both functions on that button, or maybe someone who has a camera like yours can chime in. In my case, I can assign the functions to different buttons on the back so I am not super familiar with how it works with one button.

  2. October 26, 2013 at 10:34 am —

    Thanks for this great post. I use Nikon which has the option for the AE button to also be AF. Are you familiar with this and would you use it? I have been trying to transition to using back button focusing, so I wouldn’t be able to use it as AE and get correct focus and exposure if I understand it correctly. Is that true?

  3. October 17, 2013 at 5:14 pm —

    How does AE Lock work if you are using back button focusing? So that button is now assigned a different task. I think I can make my shutter release the AE lock, but it seems like once you set your exposure and lock it, the back button focus doesn’t work while you are holding the AElock/shutter button.

    • October 17, 2013 at 9:52 pm —

      On the Canon cameras I have, the AE lock and back button focus are on two different buttons, though I know this is not the case on all Canons. On the cameras I have, if I can use AE lock on one button to lock the exposure then use the (other) back button to focus. If you do happen to have one of the Canons where both are on the same button, I would consult your camera’s manual to see how you can configure these options.

  4. October 17, 2013 at 1:49 pm —

    Hi! I currently have a Canon Rebel T3 but plan on upgrading soon. I have been struggling with the AE lock button. From articles that I’ve read, it looks like you should be able to use AE lock when in manual. But mine doesn’t. I even took it to the camera shop and the owner said I had to be in P, AV or TV mode. Is this just my camera or can you use the AE lock in manual on other cameras? Also, my camera has partial metering mode instead of spot. (When in one of the acceptable modes instead of manual) Does the camera use the center area for metering even if one of the outer AF points are selected? I ask because if my center AF is selected to meter, then I hit AE lock and try to change the AF point, I lose the AE lock. The AE lock in manual and understanding the partial metering without using the center AF point for my subject has really been tripping me up. Any help would be greatly and sincerely appreciated!!!! Thank you!

    • October 19, 2013 at 5:26 pm —

      HI Samantha, the answers to most of your questions are in this blog post and the previous one about metering. You can NOT use AE lock in manual mode. You can only use it in P, Av, and Tv. There is no need for AE lock in manual mode, because when you are in manual, you can meter, set your settings, and then recompose and your settings will not change. If you are in P, Av, or Tv, if you meter, your settings will change when you recompose because you are not in control of all of them but if you use AE lock, it will lock your settings. Metering is not connected to the focus point on Canon cameras except in evaluative metering. If you are using spot metering (or partial, as your camera doesn’t have spot metering; partial metering is the same idea but the area of the viewfinder that meters is larger than with spot metering), you are metering off a percentage of the center of the viewfinder (NOT the center focus point). I am able to change my focus point after I use AE lock, but I know some Canons have only one button on the back rather than two, and the one button is AE lock and also activates the selection of focus points, so it probably makes sense for you to choose your focus point FIRST, spot/partil meter, then recompose, focus, and shoot. Again I would recommend re-reading this article and the previous one about metering because it does contain the answers to most of your questions (and maybe some answers to some questions you didn’t even know you had, ha ha!)

  5. October 17, 2013 at 9:35 am —

    Thank you for all of the information you post – it is so helpful! I have a Nikon D5000 and I have my AE Lock button assigned for focus. If I it is set up this way then I presume locking the exposure won’t work, is that correct?

    • October 17, 2013 at 9:55 pm —

      Hi Kara. I don’t shoot Nikon and am not 100% familiar with them. If you see my answer to Rachel below re. her Canon, I know that some Canons like mine have AF and AE lock on separate back buttons but others do not. As I advised her, I would check your camera manual to see how you would work this. It may be able to be assigned via a custom function.

  6. October 16, 2013 at 4:18 pm —

    Thank you so much for this post, and the previous one too!! It explains so much to me, things I have struggled with, and have never understood. I would use spot metering, and assumed my Canon followed the focus point, and I would have horrible results. Finally, I get it! Thanks!!

  7. October 16, 2013 at 10:41 am —

    Carri, Canons meter off the focus point in evaluative metering mode only. If you are in any other mode, it is metering off a portion of the viewfinder. In spot metering, it is using the circle in the center of your viewfinder as the metering area.

  8. October 16, 2013 at 10:22 am —

    how do i know if my camera is metering off of spot or focus points? I have canon 60D?

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A Beginner’s Guide to Using AE Lock