Instagram has radically revamped its apps, including a completely refreshed camera experience for iOS, as Twitter launches its own photo filter service, in what marks a massive escalation in the battle for the social photo market.

Instagram said that its new iOS app is “the largest upgrade to our Instagram iOS camera since it was revamped just over one year ago”, with a new design that includes Instagram-themed shutter and shutter release button, a most-recent-photo preview on camera roll and an improved camera roll image selector for iPhone 5, as well as a new “Willow” filter that is also available on its Android application.

The announcement coincided with Twitter launching its own range of eight photo filters, powered by online and mobile photo editing SDK Aviary. The filters come as part of updated Twitter apps for iOS and Android, which also include the ability to see how each filter would affect your photo in a single grid view and photo auto-enhance.

The move directly pits Twitter against the Facebook-owned Instagram, in what is set to be a fascinating battle for the social photo market. Instagram has set out its stand with what it calls “significant improvements” to the look and speed of its iOS app (as well as more moderate updates for Android), while Twitter is gunning for convenience. “Starting today, you’ll be able to edit and refine your photos, right from Twitter,” the company’s senior designer Coleen Baik wrote on the Twitter blog.

Even before the two launches, the two parties had already upped the rhetoric, with Instagram last week turning off its “Cards” functionality, meaning that its photos no longer turned up in users’ Twitter feeds.