What is a focus lock in photography and how to use it?

The autofocus (AF) system of a camera works by autofocusing an object located in the center of the viewfinder. If the subject is not in the middle of the screen when the shutter release button is pressed, the subject will be out of focus because the camera will automatically set the focus and exposure for the subject in the middle of the screen. If you want to focus and expose objects that are not in the middle of the picture correctly, you need to use the "focus lock", which is a system that tells the camera where to focus.

, using Focus Lock.

First, put the subject in the middle of the viewfinder. Then press the shutter button halfway to lock the focus on the subject. When you press this button, you will hear a click or see the focus indicator (usually a green dot) on the LCD screen light up.

When the finger remains in this position, press the shutter button halfway to lock the focus.

Hold down half the shutter and reposition the subject so that it is not in the middle of the LCD. Be careful when redrawing, neither you nor the subject will leave the original position. Finally, press the shutter button completely to take a picture. By locking the focus first, the subject can focus correctly even if it is not in the middle. Since you won't just shoot the image of the middle subject, please practice this technique, so that you can compose the composition at will and focus the subject correctly in the future.

Pictures taken without the focus lock function ↑

Put the subject in the middle, press the shutter button halfway to focus on the subject.

After re-composition, press the shutter button completely to take pictures.

2. Adjust the exposure when using focus lock.

After locking the focus of the subject, the camera will also set the exposure for the subject. In other words, if the focus is locked on a very bright object, the camera will underexpose the whole photo in order to expose the subject correctly. The effect is that the whole photo looks a little dark. On the contrary, if the focus is locked on a very dark object, the camera will overexpose the whole photo, which will make the photo look slightly brighter.

Focusing on the brightest area will make the photo underexposed.

Locking the focus in the darkest area will overexpose the photo.

By locking the focus in the appropriate area, the photos are exposed correctly.

Use the focus lock function to select the object to focus on.

Use the focus lock function to select the object to focus on.

Author: John King