Scaling the magnetic field (3D only).
After the magnetic field has been specified by adding items from the menu then the field can be scaled either with a single scale factor or with 4 scale factors
If a single scale factor is used it will be applied to the total magnetic field, consisting of the sum of all the items selected from the menu of fundamental magnetic fields.
If 4 scale factors are used they will be applied to 4 components of the magnetic field, where each component consists of one quarter of the items selected from the menu of fundamental magnetic fields.
This option is intended for use with automatic focusing, but can have other uses.
For example, if 8 items have been selected then
component 1 consists of items 1 and 2, component 2 consists of items 3 and 4,
component 3 consists of items 5 and 6, component 4 consists of items 7 and 8.
It is advisable that the total number of items be a multiple of 4 -but any of these items could be dummies that have a zero current.
If the total number N is not a multiple of 4 then the formula used for the component number of item m is 1+(m-1)/(N/4).