a Bit of history and theory
Most camera phones take pictures with an aspect ratio of 2x3 or 3x4. And only camera instant photo Polaroid, Kodak Instamatic and some medium format cameras take square pictures.
Photo in a square format is much easier to compose, but it is often a more relaxed mood. It is very difficult to convey in photos like this trend. While having a wide frame, this is much easier.
In the movie, by the way, if you remember now generally used format 9:16, it is almost 1:2. And earlier to accommodate such a shot, you had to cut 40% of the area, thereby losing a lot of detail. Well, or had to use a wide field to "fit" then this narrow strip in the format of Instagram. And in your ribbon, on the page they fit into the overall picture.
But in the movie only uses the horizontal format, in photography a large percentage of the photos are made vertical. Here you had also "suffer". Now this is a more easier. Phone screens have become larger, longer and now in the ribbon you will see the entire vertical picture without reducing its lateral margins.Note: to switch completely to a very narrow vertical or horizontal photos Instagram could not (or did not want). Therefore, the restriction on the aspect ratio is now about 4:5 for vertical photo and about 2:1 for a horizontal photo
In order to use this feature if the photo is different from the square icon in the lower left corner of the button, after which pressing you have a picture be set at the maximum for that orientation aspect ratio.