Those are some of the insights the lingerie company Adore Me has learned from testing the photos of models wearing its sexy products online. For each bra, Adore Me shoots multiple versions of images to run on its website. The distinctions between the pictures might include different models wearing the same set in the exact same position, or the same model in the same set in a different position, for example. Then, like any good tech company, it tests the options to find out which one sells better.

“We see the impact of each picture in some sort of parallel process,” Adore Me CEO Morgan Hermand-Waiche told me while sitting in the chilly Metropolitan building, where this month’s photo shoot–shown here–took place. For every thousand people that come on the site, 500 will see picture A, another 500 will see picture B and over time, one will sell better than the other.

Adore Me CEO Morgan Hermand-Waiche (Right), and Simone Villas Boas, the site’s most popular model

That practice, also known as A/B testing, happens all the time on the Internet, and elsewhere. Netflix A/B tested its queue design to maximize binging; Google A/B tested the color of its ad links to maximize clicks; the Obama campaign A/B tested its website to maximize campaign donations. While it’s not all that surprising that one of the country’s fastest growing retail companies uses data to improve sales, the company isn’t quantifying the efficacy of shades of blue, but of human beings–each one as gorgeous as the last.

Adore Me certainly isn’t the only online clothing retailer that uses A/B testing to optimize product display on its website. “I would say a large majority of online retailers are doing some level of A/B testing for campaign optimization,” says Matt Helmke, the PR rep for Monetate, which provides “multichannel personalization” through A/B testing for over 300 top retail brands. Companies use A/B testing to personalize the shopping experience or test how well sales pitches work. For example, if the website knows you’re female, it will show a picture of a woman wearing its product because testing has shown that’s what women like.

But not all companies are as specific and methodical as Adore Me when it comes to each element of a photo. Of course, if a product doesn’t sell well, any online retailer might swap the image for something else. But AdoreMe subjects all of its images to testing every single month, going as far as to test one hand position against another, and in doing so has collected a trove of intel on what works and what doesn’t.

At the photo shoot, beautiful models with perfect everything glide by in stilettos. Space heaters are put out to warm the nearly nude women, while makeup artists in puffy jackets touch up their faces. The photographer, a man, has some guidelines for what works in pictures: a certain distance between the camera and the model, a specific blurriness, particular positions that sell well. Hand on hip, a popular pose among Instagrammers trying to make their arms look skinny, doesn’t resonate nearly as well as a hand on the head, for example. (That slight change can double sales, according to internal research.)