How to Measure the Mass of a Black Hole?

If we ever do get better pictures of a black hole, you might be able to tell how heavy it is by just seeing its size. So that brings us to the second question leave i had, which is, like, could i tell where the actual event horizon is? Like, at what point do you want to make sure you turn around before you get sucked in forever? Well, i wull say, turn around now. Do not take that trip to the black holeais not a good idea. Ha, ha. Don't even buy the tickets,. That's when you should turn around, right?