In the settings window of nearly every analysis feature in ZEMAX, there exists a “SAVE” button. 

Save Button - Spot Diagram Settings

Clicking this button will execute the analysis, but will also save the settings chosen to a configuration file, or .CFG file.  The configuration files are the files which describe the user-selected options for analysis windows and other settings from within ZEMAX.  The configuration file “remembers” the saved settings, so that the next time you open a new analysis window of the same type, the saved settings will be used as the defaults.

If the SAVE button is used at any time while working on a lens file, ZEMAX will construct a configuration file which is specific to that lens file.  In addition, these settings will be saved globally, either to the ZEMAX.CFG (discussed in more detail on page 3) or its own configuration file in the main ZEMAX directory.

As an example, assume you make some modifications to the Spot Diagram Settings, and press the SAVE button.  If one does not already exist, ZEMAX will construct a .CFG file specific to your lens file.  Now, each time you open a new Spot Diagram window from within the same lens file, those saved settings will be used.

In addition, ZEMAX also creates a SPT.CFG located in your main ZEMAX directory:

SPT.CFG File

It is this configuration file which controls the global default settings for the Spot Diagram.  So, if within a different lens file you open the Spot Diagram, the last set of saved settings will be used for that feature.  That is, of course, if the lens file does not have its own specific configuration file associated with it!

So, it works like this.  Any time a new analysis feature is opened, ZEMAX checks to see if there is a .CFG file with the same name as the lens file located in the same directory.  If so, then it checks to see if that configuration file contains any saved information which is specific to the analysis feature chosen.

If so, then the settings information stored in this local configuration file are used.  If not, ZEMAX will then check the global configuration file for that analysis feature, and use this information if available.  If there is not a configuration file specific to that analysis feature, then the original ZEMAX defaults are used for the settings of the chosen analysis.