Did you ever want to have different permission settings for different fields within one content type or other entity? For instance, to restrict registered users from being able to edit certain fields in entities they normally have permission to create/edit?

An example use case of this could be that registered users can create articles but can only fill in certain fields. The rest of the fields can only be filled in by the administrator or by the original author but only if and after he/she gets upgraded to a higher permission level. Oooor, you can restrict the viewing of those fields to users with certain permissions.

Examples are plentiful and I am sure you can find great uses for the Field Permission module which allows you to set the permission for each individual field to any entity in Drupal 7.

Once you install the module, you have to edit each field you want custom permission settings applied to. Or, when you create a new field of course. The great thing is that you have control over individual fields. For restricting users from viewing certain fields, you could also use the View Mode per Role module and make sure that different user roles end up viewing different combinations of fields.

Play around, hope this helps.