Pete Souza, Chief Official White House Photographer, writing on Medium:
Many followers have inquired about whether a certain photograph is taken with an iPhone or DSLR (digital single lens reflex camera). In choosing the photographs for my year on Instagram, I decided to select only iPhone photographs that were captured in the square format on an iPhone. For many purists, the square format was the original inspiration for Instagram. And I certainly admire those that continue to post only square photos taken with a smart phone.
My approach to my Instagram feed continues to be all square photos are taken with an iPhone, and full-frame horizontals and verticals are taken with a DSLR (usually a Canon 5DMark3, but I’ve also posted some from Sony, Nikon and Leica cameras).
There's a beauty about Instagram's original square format – a creativity derived from the boundaries of constraint – that I still see as the purest expression of mobile photography. Some of Souza's photos are somewhat staged, but the majority of them have taken on the spur of the moment, where a smartphone makes for an excellent storytelling tool. Fantastic shots. I love the last one.