Earlier this year, Twitter snatched up streaming-video app Periscope for an estimated $50 million. The buy was Twitter’s defensive strategy against Meerkat, another streaming-video app, as well as the behemoth Snapchat, now valued at $16 billion. While the growing pool of video-oriented apps seems to be just another case of tech giants duking it out over venture capital and digital real estate, it’s actually causing headaches for veteran video makers, from movie moguls in Hollywood to ad men in New York. Why? Because Meerkat, Periscope, Snapchat and others are subverting the oldest rule of filmmaking: They’re forcing users to shoot vertically.

“As a filmmaker, shooting vertical actually hurts me,” says Joanna Hausmann, a digital-video writer-producer in New York. “But when I do a video for Snapchat, I shoot vertically because I know that’s how people will accept it.”

The vast majority of videos for apps are filmed and watched vertically simply because that’s how people hold their phones. But when viewed on any other platform—whether a tablet, an iMac or your 60-inch HD TV—vertical videos are bookended by distracting black bars. Moreover, these vids tend to have low resolution, last only a few seconds and have little to no production value.

Such cringeworthy attributes have long been common in amateur film efforts, but thanks to the popularity of these apps, they’re quickly becoming the norm for videos by experts too. According to Hausmann, who creates content for Univision and Bedrocket Media, the shorter, grainier and more amateur-looking, the better, especially when it comes to ads.

“The moment millennials recognize an ad as an ad, they switch off,” she says. “Commercials now need to look like something their friend shot.” And the fact that highly sought-after millennials are the bread and butter of global brands such as Samsung, Disney and Burger King means that awkward vertical videos will only become more commonplace. Even YouTube tweaked its Android app to eliminate the black bars; vertical videos now get automatically resized to fill your screen when played.

“We hear a lot of the industry saying a platform like Snapchat is just a fad, but you have to have vision,” says Carlos Roncajolo, who teaches digital and social media at Miami Ad School and heads digital content for marketing firm Cheil Worldwide. “We ask ourselves all the time, ‘How can a company like Samsung use Snapchat?’ Whoever answers that question wins the game.”

Could iPhones and the pursuit of greenbacks be the ultimate undoing of the oldest law of cinematography? Some point to basic human physiology for the answer.

“The world is aligned horizontally. Our eyes will never be stacked on top of each other,” says Adam Lisagor, owner of Los Angeles–based Sandwich Video, which produces TV commercials. “I have a strong respect for the language of cinema that exists already. I can safely say that mobile-phone screens are going to go away sooner than human vision is going to reorient itself.”