Use the Nikon D3400's Shutter Button to Lock Exposure and Focus

You can customize the behavior of the Nikon D3400's shutter button as far as the button's impact on the autofocus and autoexposure systems. Again, start by opening the Setup menu and choosing the Buttons option. On the next screen, the last two settings relate to the shutter button. Here's what you need to know about each setting:

• Shutter-release Button AE-L: This option determines whether pressing the shutter button halfway locks focus only or locks both focus and exposure. (AE-L stands for autoexposure lock.) At the default setting, Off, you lock focus only when you press the shutter button halfway. Exposure is adjusted continually up to the time you take the shot. If you change setting to On, your half-press of the shutter button locks both focus and exposure.
• AF Activation: At the default setting, On, pressing the shutter button halfway initiates autofocusing. If you change the setting to Off, pressing the shutter button halfway fires up the autoexposure system only.