Do professional photographers have to keep their eyes open when taking pictures?

You can choose freely. Turning a blind eye has its advantages and disadvantages, and there is no fixed standard.

Both eyes are open.

It can provide the relationship between the whole and the parts, which is convenient for the use of lens language, but it may distract attention.

2. Close one eye?

Being able to pay more attention to the viewfinder has many inconveniences and even potential dangers.