Controlling who can contribute?

The office I work in is currently working on moving from a software package that's become too expensive to Omeka. The idea is to transfer all the existing images over to Omeka and allow the right people to add images to the collections. Since these collections are archives of specific departments on campus, we'd like to control who is able to add to them. I guess that's not really in the spirit of Omeka, but it's what they're wanting to do.

The only way I've found so far to do this is to make the default collection private, which works, but is there a way to make the contribution plugin accessible only to people with the user role of contributor (or above)?

Here's the site we're using to figure stuff out:

Thanks in advance,

Instead of using the public-facing contribution plugin, have you considered giving users contributor user roles so that they can add items via the Omeka admin interface? Do you need to limit the contribution of users to specific collections?

Thanks. I got some clarification on how the administration wants it to work. We want to have a contemporary printmaking collection. We'd like professional printmakers from all over the world, really, to be able to contribute to the collection, but not just any average Joe. We could do what you said and deactivate the plugin, but then we would need some sort of screening process to decide if we should let them add items, which could be really inefficient. We could also change the contribution form to send the message that we're only looking for a specific type of contribution, but that wouldn't necessarily work all the time, either. I'm not sure there's a good answer to this problem, but I appreciate your help and suggestions.