Twitter has been working hard over the last year to make photo sharing a core part of its product. It took over the photo-hosting role from third parties and gained deep new integration with Apple’s iOS, among other initiatives. But there’s also a big new winner coming up on top of its developer platform — mobile photo-sharing app Instagram.

New stats provided to us by social photo aggregator Pixable show how this trend played out at the South By Southwest conference in Austin last weekend. The startup tracked all photos tweeted straight from Twitter or via Instagram, that contained relevant hashtags like #SXSW and #SXSWi.

It found that out of the 63,000 photos uploaded, approximately two-thirds came from Twitter itself and one third via Instagram.

While the study didn’t look at any other photo services that share through Twitter, the number here is still surprisingly large. Instagram, which provides easy ways to alter photos and then share them to social networks, only had around 12% of the total market as of last November. One would have expected it to have less than a third of the usage last weekend.

So what’s next? SXSW is heavily attended by people from around the world who consider themselves influential early adopters. The heavy use they gave Instagram could mean they’ll be helping to evangelize the app later on.

The Instagram market numbers are also likely lower than they will be soon. It is only available for iOS now, but the forthcoming Android version will open it up to many more users (people who Twitter itself already has access to). And then there’s the already strong growth on iOS, where it has nearly doubled to 27 million users from 15 million in the last six months alone.

So, hopefully Twitter is comfortable having this new third-party app make such big waves in an area that it considers a core part of its product.

And with that, I’ll leave you with an infographic. I may hate the things, but this one does a nice and simple job of telling the story without all the crappy clipart that many others have.