From:  Michael Gibson
4570.2 In reply to 4570.1 
Hi Felix - setting a filter prevents objects from being _selected_ , not necessarily from being modified if they were already selected before you set the filter.

So if you don't want existing selected objects to be targeted by whatever command you're going to run next, you'll want to deselect everything first before you go to set the filter.

Basically the filter is something that controls selection, when it is set only objects that match the filter will be targeted for selection actions, including selecting things with the mouse, select all, using the scene browser to select things, etc...

By not clearing the existing selection it allows for things like building up a particular selection one step at a time like filter in a few different steps to get the final selection that may have some combination of things in it. If filtering did not allow for the previous selection to come through stuff like that would not be possible.

Please let me know if this does not explain things - if you are seeing something different than what I am describing it would help if I could see an example file.

- Michael