Which is the most important, portrait shooting, preview of depth of field, pre-elevation of reflector and spot metering? What are the other two main functions?

Spot metering and preview of depth of field are very important for portrait shooting.

Portrait photography needs to achieve different artistic effects. Spot metering can capture the ideal exposure value and contrast between light and shade, which is very important for creation.

Portrait photography needs a lot of blurred images, and preview of depth of field can accurately blur the background, so that the viewfinder is the same as the depth of field of CMOS, and the background blur meets its own requirements.

The pre-lifting of the mirror is to reduce the impact of shutter vibration and has little effect on portrait shooting.