Advanced activerecord validation

model validations aren't tied in any way to controller actions, and
you shouldn't really have a need to this. what i think you might want
to use is the :on option

validates_presence_of :image_1, :on => ...

:save - default, validates anytime model is saved (insert or update)
:create - only validates when model is created (insert)
:update - only validates when model is updated (update)