Instagram photo social network has partnered with Hipstamatic app for iPhone to allow users directly upload their photos to Instagram from their phones.

Photo: Instagram interface within Hipstamatic app, from www.fastcompany.com

Hipstamatic is a photo-filtering iPhone app that allows users to make creative photos. Now has 4 million users who upload 48 million photos a month. Through the partnership with Instagram, Hipstamatic hopes to increase the number of its users.

Fast Company interviewed Hipstamatic cofounder and CEO Lucas Buick who told them that Instagram, with its 27 million users, has now become the primary photography hub.

“When we launched, it was all about Facebook and Flickr and Twitter, and now we’re seeing a huge shift in our user base toward Instagram,” Buick said. “We’ve never been a social networking company, but we clearly benefit from social networks. So this will be the first app outside of Instagram that lets you into their network. That’s pretty cool for us.”

The photos that users will direct from their iPhones via Hipstamatic will be tagged “Taken with Hipstamatic,” when they appear on Instagram. The partnership has additional marketing plus for the app, as when users see and click on the #Hipstamatic tag on Instagram they will be able either open Hipstamatic or download it in the App Store for $1.99.

It is the first time Instagram has opened up its API to a third party and the company expects it will bring good benefit.

“It’s a step in a direction that we’re testing out. We’ve been very careful about making sure that Instagram photos are about what’s happening right now in your life, and we want to allow for more of those photos to end up on Instagram regardless of where they’re taken,” commented Buick.

Earlier this year, Levi’s used Instagram to launch its casting.