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How to Customize the Canon T6 AE Lock Button for Better Exposure Control
The small asterisk (*) button on the back of your Canon Rebel T6 might be the most underused control on the entire camera. By default, it locks your exposure so the camera holds a specific brightness level, even if you recompose your shot. But the Canon T6 AE lock button can actually be customized to behave differently depending on how you shoot. Understanding what it does, and how to change it, gives you significantly more control over your photos.
What Does AE Lock Actually Do?
AE stands for Auto Exposure. When you half-press the shutter button, your T6 simultaneously focuses on your subject and meters the light in the scene to determine the correct exposure settings. Those two actions happen together, linked to whatever your focus point is aimed at.
The problem arises when you want to expose for one part of the scene but focus on another. For example, imagine you’re photographing a person standing in front of a bright window. If you focus on the person, the camera might meter off the bright background and underexpose your subject. AE lock solves this by letting you lock the exposure reading separately from the focus point.
Here’s how it works in practice: point your camera at a mid-toned area with the lighting you want to capture, press the AE lock button (the asterisk), then recompose to frame your actual shot. The exposure stays locked at the reading you chose, regardless of where the lens is now pointed.
Default AE Lock Behavior on the Canon T6
Out of the box, the Canon T6 assigns the AE lock button to lock exposure independently from the shutter button. When you press the asterisk button, a small asterisk icon appears in the viewfinder confirming the lock is active. The lock holds for about four seconds, or until you press the button again.
Meanwhile, half-pressing the shutter button handles both autofocus and metering. This means you have two separate controls: the shutter button for focus and initial metering, and the AE lock button for holding exposure independently.
Customization Options: Custom Function Settings
The T6 lets you change how the shutter button and AE lock button interact through Custom Functions. To access these settings, press Menu, navigate to the Setup menu tabs, and find Custom Functions (C.Fn). Look for Custom Function 7, which controls the Shutter/AE lock button behavior.
If you are still exploring options, our Canon T7 vs Canon T6 guide is a solid next read.
You’ll see several options. Each one changes the relationship between the two buttons in meaningful ways.
Option 0: AF/AE Lock (Default)
This is the factory setting. Half-pressing the shutter button activates autofocus and metering. The AE lock button locks exposure independently. This works well for most shooting situations where you occasionally need to lock exposure but usually let the camera handle both focus and metering together.
Option 1: AE Lock/AF
This option swaps the primary functions. Now the AE lock button activates autofocus, and half-pressing the shutter button only meters and locks exposure. This is commonly called “back-button focus” and it’s popular among experienced photographers.
Why? Because it separates focus from the shutter button entirely. You focus by pressing the back button with your thumb, then shoot with your index finger whenever you’re ready. The focus doesn’t reset each time you press the shutter. This is particularly useful for subjects that stay at the same distance, you focus once, then shoot multiple frames without the camera hunting for focus between each shot.
Option 2: AF/AF Lock, No AE Lock
With this option, half-pressing the shutter activates AF as normal, and the AE lock button temporarily stops autofocus from adjusting. There’s no exposure lock at all. This is useful when you’re tracking a moving subject in AI Servo mode and want to temporarily freeze the focus distance, press the back button to hold focus, then release to let the camera resume tracking.
Option 3: AE/AF, No AE Lock
This option makes the AE lock button activate both autofocus and metering simultaneously, while the shutter button does neither until you fully press it to take the shot. Again, no independent exposure lock is available. This is another variation of back-button focus, but with metering tied to the back button as well.
This topic ties into our Canon EOS Rebel T6 guide, which covers the next steps.
Practical Use Cases for Each Setting
Portraits with tricky lighting: Stick with the default (Option 0). Meter off your subject’s face, press AE lock, then recompose for a more creative framing. The exposure stays locked to skin tones even if the background is much brighter or darker.
Sports and action: Try Option 1 (back-button focus). Focus on the player or subject with your thumb, then fire bursts with the shutter button. If the subject stops moving, your focus holds without re-engaging. If they start moving again, press the back button to resume tracking.
Landscapes: Option 0 works well here too. Lock exposure on the brightest part of the sky, recompose to include the foreground, and shoot. This prevents the sky from blowing out to white.
Wildlife and unpredictable subjects: Option 1 shines here. Focus on the animal with your thumb when it pauses, then shoot whenever the moment is right. If it moves, press the back button again to re-engage focus. You never miss a shot because the shutter button was busy hunting for focus.
How to Set Up Back-Button Focus on the Canon T6
Back-button focus is the single most popular AE lock customization, so here’s a quick walkthrough. Go to Menu, navigate to Custom Functions, select C.Fn 7, and choose Option 1 (AE Lock/AF). Press Set to confirm.
Now your thumb controls focus via the asterisk button, and your shutter button handles exposure metering and firing only. It takes a few shooting sessions to break the habit of half-pressing the shutter to focus, but once you adjust, most photographers never go back. The control it gives you over focus timing is genuinely transformative.
The Canon T6 AE lock button is a small control with outsized impact on your shooting experience. Spending five minutes in Custom Functions to match the button behavior to your style can make the camera feel like a completely different tool.
