Depth of field This is how far the object can move towards or away from the lens while still maintaining acceptable image quality The trick is in defining "acceptable " It really does depend on what results you are trying to achieve We hope to make your work easier by using two different depth of field specifications that will be defined below Honest, more is easier in this case
The depth of focus is the distance over which the focussed beam has about the same intensity, it is defined as the distance over which the focal spot size changes -5%~5%