Lock focus and exposure so your video stops pulsing
If your video gets brighter and darker as you move, or keeps refocusing on the background, the camera is re-measuring the scene many times a second. Locking it tells the phone to stop guessing.
On iPhone
In the Camera app, press and hold on your face until AE/AF LOCK appears. Then drag the sun icon up or down to make the picture brighter or darker. The lock holds until you tap somewhere else.
In TikTok's own camera you can tap to focus, but the lock is less reliable. For important talking videos, film in the Camera app and upload.
On Android
Most Android camera apps lock on a long press as well; Samsung shows a lock icon, Pixel shows a padlock or a slider. If yours does not, look for Pro or Manual mode, where focus and exposure can be set by hand.
In Pro mode set ISO as low as the light allows and leave shutter speed around 1/50 for 25 fps or 1/60 for 30 fps, which keeps motion natural.
When locking helps most
Talking to camera with a bright window or lamp in shot. Product videos where your hand moves in and out of frame. Walking clips where the sky keeps entering the picture.
Re-lock every time the light changes. A lock set by the window is wrong once you walk into the hallway.
Check before you film a batch
Record five seconds, play it back, and look at your face and the background. If the face is a little dark, raise exposure slightly; it is easier to fix a dark image than a blown-out one.
Frequently asked questions
Why does my video keep getting brighter and darker?
The camera is re-measuring the scene many times a second as you move. Locking focus and exposure tells the phone to stop guessing.
How do I lock focus and exposure on an iPhone?
In the Camera app, press and hold on your face until AE/AF LOCK appears, then drag the sun icon to adjust brightness. The lock holds until you tap elsewhere.
Do I need to re-lock exposure when the light changes?
Yes. A lock set by a window is wrong once you walk into a darker hallway, so re-lock each time the lighting changes.