As Tola Vann goes about his day, his cellphone -- perhaps more often used as a camera -- is never far away.

He spots a neat architectural detail. He takes a picture. A colorful leaf, an interesting landscape or a particularly moody cloud? Snap. Snap. Snap.

Then, with a few quick taps on his phone, he adds special effects and posts what he has seen on Instagram, a mobile photo sharing app, for millions of people worldwide to see.

"Instagram has kind of sparked this whole passion for photography," said Vann, 33, of St. Paul. "It's also sparked more of an awareness of things around me."

He's not alone in his self-described "infatuation" with the increasingly popular photo-driven social media platform. Just searching for photographs specifically tagged "Minnesota" recently yielded more than 140,000 results on Instagram. Never mind the millions of other pictures of animals, food, nature and kids.

"It's kind of riding the train toward being the popular social network right now," Vann said. "It's still gaining steam."

Instagram has been around about two years, first attracting design and photo enthusiasts for its array of filters that give snapshots a more stylized look.

Then Instagram hit the headlines when Facebook bought it for nearly $1 billion. The app, first available for Apple mobile devices before adding an Android version in April, is free to download and use.

Instagram users now number in the tens of millions. A study by the Pew Research Center found that 12 percent of online adults use it, and it's particularly popular among the younger set.

Digital market research firm comScore in September ranked Instagram more popular than Twitter, noting that the photo app had 7.3 million daily active users in August, compared with Twitter's 6.9 million.

Seth Lewis, an assistant professor at the University of Minnesota who has studied social media, said Instagram's success comes in part from its mobile-device focus.

Unlike Facebook, which started as a website and is now trying to improve its mobile app, Instagram started as an app and has very little info -- not even a photo gallery -- on its website.

"It seemed to capture the zeitgeist of the smartphone era," Lewis said. "The mobile platform is becoming the go-to platform for information creation."

From Instagram, users can post photos to Facebook, Twitter, tumblr and other platforms. Other websites and apps such as allow users to view galleries and print their photos. Others like Vintique add more filters that change the appearance of photos.

Lewis said Instagram fits the criteria of the apps with the most staying power: It solves a problem and gives people a new avenue for excitement in everyday life.

"We all had these phones in our pockets with really incredible cameras, but not a lot of ways to take photos and share them fluidly," he said.

For Carrie Hackney, 27, Instagram is appealing because it's a break from more contentious corners of the digital world.

"It's kind of a happy place, unlike Facebook where there's drama and political talk and all the stuff there you can't necessarily avoid," she said.

But there are downsides to the site's increasing popularity, users note, including more "followers" who are actually pushing spam, and a larger quantity of pictures of lower aesthetic quality (think: too many cat or blurry kid pics).

Like any social media site, it requires common sense about what's appropriate or safe to post for all to see.

Instagram users can keep their accounts private, allowing only followers they approve to see their pictures. But the default setting is public and the app thrives on sharing and mutual appreciation among complete strangers.

For that reason, enthusiastic Instagram user Katy Brandl, 26, doesn't post pictures that show her son's face. She's also cautious about locating pictures on a map -- an optional feature -- especially when photos are taken at home or posted in real time.

"You have to be careful," Brandl said. "You don't know who's watching you and they know where you are all the time."

The intimate feel has worked well for local museums and businesses that have followings on Instagram. The Walker Art Center uses Instagram to give a peek behind the scenes, including shots of artwork being installed.

Tamas "Zen" Pomazi, co-founder and master cobbler at Greenwich Vintage, a Minneapolis company that refurbishes shoes with colorful soles, regularly posts shots showing details of his work and the finished products.

He said he doesn't post prices or make an overt sales pitch with the photos, but tries to illustrate the hard work and originality of the shoes.

"I'll post something, I'll get a bunch of likes and then one person will comment saying, 'I really want this, how do I get it?'" said Pomazi, who makes a point of responding to individual comments. He's gotten inquiries from and made sales to places as far away as Japan, Italy and Australia. "We have a worldwide audience now because of Instagram."

Katie Humphrey • 612-673-4758