In most contexts, if someone asked me to take a photo of my bust using their iPhone app, I would say no.

But ThirdLove, a retail startup that promises to calculate a woman’s bra size using just two tank top-clad iPhone selfies, has all the signs of a legitimate business: Its cofounder, Dave Spector, is a former partner at Sequoia Capital (he started the company with his equally qualified wife, Heidi Zak). They’ve raised $5.6 million from investors whose names I recognize. And a NASA scientist heads up the engineering team.

So unless this is an overly elaborate plan to relaunch the creepshots subreddit, I figure it’s safe.





The current version of the ThirdLove app (it’s still in private beta) features a tutorial in the voice of a polite but firm woman who sounds a bit like my grade school principal. As instructed, I stand in front of my mirror with my phone at my belly button. “Slightly raise right end of the phone,” she says. Then “slightly raise left end of the phone.” Then, “slightly raise right end of the phone.” After about 50 more rounds of this, there’s a gratifying “Good job” and a countdown to the photo.

Instructions on the screen ask me to line up a box with the iPhone in the photo and to place a line on my chest. Then the principal voice walks me through the same process for a photo from the sideways perspective.

This is where the technology, about which Spector would “prefer not to get into too much detail,” comes in. Ara Nefian, a senior scientist with the Intelligent Robotics Group at NASA Ames Research Center, led the team that developed it. His explanation isn’t much more specific. He says the back end “involves several methods of advanced computer vision, body modeling, and machine learning” and uses the iPhone in each photo as a “calibration object” for estimating the parameters of the camera. Once those parameters are known, it’s possible to accurately measure a 3-D object—in this case, the human body—using a 2-D image.

The result from the user’s perspective is a customized store filled with ThirdLove products in her size. What is that size? It doesn’t say. The presumption is just that everything fits. I won’t find out whether that’s actually the case until I receive the bra in the mail. (Update: It fits)