Hi cinsng,
Thanks for posting in Apple Support Communities. We'd recommend checking your settings as that may be a factor here. For example, check to see if this happens with HDR enabled or disabled. The following is from Adjust HDR camera settings on iPhone.
"Turn off automatic HDR
By default, iPhone automatically uses HDR when it’s most effective. On some iPhone models, you can manually control HDR instead.
On iPhone XS, iPhone XR, iPhone 11 models, iPhone SE (2nd generation), and iPhone 12, go to Settings > Camera, then turn off Smart HDR. Then from the camera screen, tap HDR to turn it off or on."
If you are taking photos in low light situations, the following from Take great photos and videos.
"Shoot photos in low light
On supported models, Night mode automatically takes bright, detailed photos in low-light settings. When turns yellow, Night mode is on. Tap the Shutter button, then hold your iPhone still to capture the shot. To experiment with Night mode, tap, then move the slider below the frame to adjust the exposure time."
Take care.