Originally Posted by Baltipal
I've heard x10 is the optimum for the depth of field.
You heard wrong. The best possible DOF would be achieved with the lowest mag available. DOF is also increased by reducing the size of the front objective. 10x is often used as a compromise between DOF and actually being able to make the targets appear as large as possible. It also happens to be the mag setting where many scopes are "true" as far as mil-dots go. Increasingly, people are using lower mag, smaller objective scopes in an effort to maximize DOF.