It's been one month since portrait and landscape photos were allowed on Instagram, and — much to my surprise — all hell has not broken loose. In fact, it's been a pretty great month for browsing Instagram.

Instagram has been about square photos since it launched nearly five years ago. The app singlehandedly made square photos cool and iconic once again, and it was puzzling trying to imagine a world in which "an Instagram" did not mean a square filtered photo. My personal fear was that all of our feeds would become clogged with poorly lit portrait selfies. And some days they are — it just turns out there's reason to like them.

Photography traditionalists across the globe have been lamenting the rise of portrait, which phone owners are increasingly using as the standard for shooting. There's good and obvious reason for why this has happened: we hold our phones upright — not sideways — and a portrait photo takes up the entire screen. Big photos just look nice, even if portrait framing isn't optimal for many of the uses it's now put up to, from group selfies to, yes, landscapes.

I've been as critical as anyone. But seeing portrait photos fill up my feed over the past several weeks has changed my mind. I'm not about to start shooting all portrait — but portrait is absolutely the best format for Instagram.

Portrait works on Instagram for the same reason that people enjoy seeing it in their phone's camera roll — simply because it's big. The effect is particularly dramatic on Instagram, because portrait photos appear in the same vertical line as skinny landscape shots. As you browse your feed, suddenly a huge image will begin to fill almost the entire screen. In many cases, it can make a photo far more awe-inspiring than a similar shot placed in any other crop. It's gotten to the point where I'm getting upset when some photos aren't posted in portrait.

And I don't think there's any reason to be beholden to Instagram's square-shaped roots. If anything, portrait photography creates an experience closer to what Instagram was originally like. Why was Instagram based on square photos at first? Because square photos are what looked good on the early iPhones' now-tiny 3.5-inch display.

If you look back at screenshots of Instagram's earliest versions, you'll see that square photos took up basically the entire screen. Almost everything else was the app's necessary interface. That looked great on a tiny phone with a 4:3 display. But now we use huge phones with 16:9 displays. Since the iPhone 5 (and its launch on Android), Instagram's square photos have been surrounded by white space. It's by no means a bad look, but it doesn't create the same effect of a single photo overwhelming the screen.

Image left credit TechCrunch, from one of its first articles about Instagram in 2010.

"I think [portrait] is probably, going forward, going to be the most popular format on Instagram," Kirsten Alana tells me. Alana is a travel and lifestyle photographer who's been using Instagram as a platform to share her work since, she says, about two months after the app launched. In the time since, she's built up a following there of close to 150,000 people. "Already, I've noticed that when I post portrait photos they do better than my square images, or they are certainly comparable, and they definitely do better than my landscape photos," she says.

Alana suspects that portrait is succeeding for the same reason that landscape photos — which, on Instagram, look more like narrow thumbnails than dramatic landscapes — have been less effective. "I think people are frustrated because their phones are small to begin with ... but they also still want the photos to be as big as possible," she says. "That's why they favor apps and other methods of viewing that give them the most real estate for any media ... They want to see a photo or video as big as they possibly can."

Instagram declined to share data on the interaction with or overall growth of these new formats, but it did tell The Verge that portrait has been "slightly more popular" than landscape. That at least slightly speaks to my own prediction, and Alana's as well. People like portrait photos on phones, and Instagram creates an environment where they look great. Maybe Instagram needs the diversity of landscape, square, and portrait for any one of them to have meaning. But the next time you want to wow me, post portrait.