Topic: Find all excluded in has_many :through

Hi, newbie question - I have the following models:

Person
has_many :photos, :through => :configurations
has_many :configurations
 
Photo
has_many :persons, :through => :configurations
has_many :configurations

Configuration
belongs_to :person
belongs_to :photo

If I want to find all photos associated with a person, I just do
@person = Person.find(params[:id])
@photos = @person.photos.find(:all)

My question is, how do I find all the photos that are NOT associated with that person?
I tried doing it through the configurations table, but I think I'm looking in the wrong direction.

Any help?

Re: Find all excluded in has_many :through

Configuration.find(:all, :conditions => ['person_id <> ?', params[:id])

Should give you all configurations not associated with a given person. Then you should be able to iterate it to pick out photos (possibly, using uniq to remove duplicates).