Perhaps one of the most important decisions Apple made with Aperture 1.5 is to allow third-party developers to extend the application with a new plug-in architecture.

While only available for about a month Apple said the response by developers has exceeded their expectations.

"We knew that there would be a lot of interest, but we received 150 emails from individuals, companies and organisations that all want to develop plug-ins for Aperture," said Richard Kerris, Apple's director of professional photography partnerships.

"We are all pleasantly surprised with the companies that want to develop plug-ins. It really makes this a powerful application for whatever type of photographer you are."

Apple launched its Aperture API with several big name partners including Getty Images, iStockphoto, Pictage, Flickr, PhotoShelter, DigitalFusion, Soundslides and Connected Flow. This week at PhotoPlus Expo in New York another company, ExpressDigital, released its plug-in for Aperture.

ExpressDigital's Aperture plug-in allows photographers to directly upload photos to, a virtual storefront for professional photographers.

DigitalFusion is also offering a new Aperture plug-in. DF Studio Link allows direct upload of images from Aperture to a DF Studio account.

"In the professional workflow arena, no application is an island - it depends how it can be extended," said Apple's Kerris. "We are seeing the new technology out there for digital photographers becoming part of our workflow. It ties Aperture into the centre of the universe for digital photographers."

By allowing developers to offer plug-ins to extend Aperture, Kerris said that it allows the photographer to focus on what's really important to them - their craft. Apple is not leaving all of the development to third-parties - the company will also continue to make plug-ins, according to Kerris. For example, a new plug-in from Apple ties Aperture more closely with Final Cut Studio, Apple's professional suite of video applications.