Longer camera exposure time

I would like to know about the exposure time setting of the iPhone camera.

According to the specifications of the back camera of my iPhone 8, the maximum exposure time is 1/3 second, but I would like to expose for a longer time.
Looking at the camera app on the App Store, it seems that there are some apps that can expose in seconds, but how is it realized?

I tried to use AVFoundation's activeVideoMinFrameDuration, activeVideoMaxFrameDuration, and setExposureModeCustom, but could not find the solution.

If anyone has any knowledge about this area, please help me.
Best regards,
Longer camera exposure time
 
 
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