Log is based on 19 / 20, and the true number is 1 / 2. What is it

Log is based on 19 / 20, and the true number is 1 / 2. What is it

Bottom changing formula
=lg(1/2)/lg(1920)
=-lg2/(lg19-lg20)
=-lg2/(lg19-lg2-1)
That's it. The approximate value is about 13.5134