I'm not for or against that new sensor. But I would like to add something about 2:3 portraits/images:
Mona Lisa by Leonardo DaVinci is 2:3 (77x53cm)
Madonna dell Granduca by Raffael is 2:3 (84x55cm)
The Inspiration of Saint Matthew by Caravaggio is 2:3 (292x186cm)
Sure, there are 3:2 portraits (and even ones beyond 2:1 for full body portraits). On the other hand there are many 5:4 and 4:3 landscapes: a lot of Ansel Adam's work for example, and he was willing and able to crop heavily in order to improve a composition.
But when I looked through large collections of art books that give painting dimensions and studied the distribution of aspect ratios:
- The great majority are between 5:4 and 3:2, with the most common shape ("mode") being about 4:3 for verticals, 7:5 for horizontals.
- Even with horizontals, the great majority of paintings in my survey were a bit less wide than 3:2, and a bit less wide than 3:2 was more common than shapes wider than 3:2.
- Outlier shapes seem more common than with photographs, running from square and 6:5 to 2:1, 3:1 and beyond: canvas shape choices are more flexible than film frame shape choices, and there are no "image circles" to work within.
Surely a good choice for a photographer working with a single camera is a shape near to that particular photographer's most common choice, or in the middle of the range of his or her common choices, to minimize percentage loss to cropping in either direction.
Those who must suffer under AD's that might wish to change an image from horizontal to vertical or vice versa probably benefit from a fairly square shape. Or otherwise, might need to learn "shape bracketing"!
With film there was an additional constraint, as there was a big cost advantage to staying with the existing 135 roll film with its 24mm emulsion width. Within that constraint, the wider 3:2 shape of 36x24mm includes as crops all less wide shapes like 5:4 (30x24mm) and 4:3 (32x24mm). Changing to a less wide frame shape could only be achieved by effectively imposing a crop at the sides of every frame compared to the 36x24mm option.
120 roll film went mostly in the opposite direction with frame shapes, but perhaps for similar reasons: even when using the 56mm roll width as the long dimension was sufficient, greater flexibility was achieved from a greater value for the other dimension, so it makes sense that sizes bottomed at 56x42mm and 4:3 (645) rather than going down to about 56x37mm for 3:2 shape.
But we are getting the last and smallest of these shapes in MF now with the Leaf/Dalsa sensor, probably due to sensor cost constraints.