How to lock the zoom distance?

I used to know how to do this, but I totally forgot how to do it due to me not needing or wanting to do this recently.
In some games, you cannot zoom out a lot like you normally can, in my game, if you zoom out a lot you see some of the other things in my game that you're not supposed to see because you are supposed to be teleported to them and not see any exterior of them. I KNOW there is a way to change this as I have seen games do this, can somebody tell me how? (to sum it up, I just need to know how to change the maximum and minimum zoom distances, I assume its easy but I forgot how)