The content of image archives changes rapidly. This makes the traditional separation of ontology development and image annotation steps no longer feasible. In this paper, we present an approach, termed ImageNotion that allows for the collaborative development of domain ontologies directly by domain experts with minimal ontology experience. ImageNotion is both a methodology based on the idea of the ontology maturing model, and the name of the tool supporting this methodology. ImageNotion embeds the creation of ontology entities, termed imagenotions, into the work process of creating semantic annotations of images and their parts. Both the creation of imagenotions and the creation of image annotations are visual, user friendly processes, implemented by a web application that integrates all of the required functionality in one consistent framework. Besides the theoretical concepts, this paper also presents the results of our evaluation of the system with experienced image annotators and l...