What does AF-L do on a Nikon, and why use it instead of half-pressing the shutter?
Asked 12/30/2015
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On a Nikon D5300, I’m trying to understand the AF-L function on the AE-L/AF-L button. In AF-S, half-pressing the shutter already locks focus, so AF-L feels redundant. In AF-C, the camera keeps refocusing while the shutter is half-pressed, so I’m unsure why a separate focus-lock control is useful. What practical advantage does AF-L provide over simply half-pressing the shutter and recomposing?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
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If the camera is set to AF-C, then the concept of locking focus at a particular object/distance makes no sense.
On the contrary: if the camera is set to continuous autofocus (AF-C), it's going to constantly adjust the lens to keep focus while the shutter button is half-pressed. That's great for moving subjects, like athletes. But that's not always what you want. There are times when you're shooting in AF-C, but you'd still like to lock focus and then recompose, and that's exactly what the AF-L button does for you.
Consider, for example, that you're shooting a penalty kick at a soccer game. Maybe you'd like to take a shot where the ball and goalie are in focus, but timing is critical, so you want to pre-focus and maybe recompose as well. So you focus on the cross-bar or goalie, hold the button, and then wait for the ball to arrive at the goal plane. You could do that with single shot (AF-S) mode, of course, but switching between AF modes all the time isn't exactly convenient. AF-L is like a shortcut that temporarily modifies the normal AF behavior.
Isn't it a redundant functionality assigned to a button which could be better used for some other purpose?
Well-designed tools often offer more than one way to do things. Another example: you can configure many DSLRs to use one of the buttons on the back of the camera to activate the AF system instead of relying on the half-pressed shutter button. Also, you configure the AE-L/AF-L button for just AE-L if autofocus lock isn't useful to you.
Originally by user4262. Source · Licensed CC BY-SA 4.0
user4262
10y ago
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AF-L is useful because it lets you control focus independently of the shutter button and exposure lock. That gives you more flexibility than a half-press.
In AF-C, AF-L is especially helpful: the camera would normally keep refocusing while you half-press the shutter, but AF-L lets you stop autofocus at a chosen distance so you can pre-focus, recompose, and wait for the right moment.
In any AF mode, AF-L can also help you avoid locking exposure when you only want to lock focus. With a half-press, many cameras tie focus and exposure behavior together depending on settings. A separate AF-L button lets you choose when autofocus is active without changing other controls.
It’s also part of a broader workflow benefit: separating AF/AE from the shutter gives faster, more fluid control without diving into menus.
That said, recomposing after focus lock is not always perfect, especially at wide apertures where recomposition can shift the plane of focus enough to miss slightly. So AF-L is not just a duplicate of half-press behavior; it’s a separate control for more deliberate handling of autofocus.
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