1. A little exercise for you.

   Pick up a book or magazine (A4 or A5 portrait format) and sitting comfortably, read the top line.

   Then read the bottom line; taking notice of what you do in between.

   And if you didn't tip the book back, and lift the bottom edge higher to read it; you're 1 in a billion.

   You hold paper media -- books, magazines, letters and newspapers -- in your hands, and adjust their distance and angle to suit the part of the page you are reading. This is automatic and mostly goes unnoticed until you start to think about it.

   And that is the problem with portrait mode screens, you are constantly having to adjust the tilt and your distance from them.

2. I wish I could find references to the VDU/UI ergonomic design work done by Northern Telecom and other back in the mid-80's, but it predates the time when stuff started to be made available online. What follows is only a few of my recollection of a raft of stuff I read back then.
   • The sizes and format of paper media were not designed for ergonomic ease of use.

     Broadsheet newspapers were 12" wide, because the rolls were 48" wide (or 13.5"/54") and they fold them in four. Everything to do with the convenience of the paper manufactures (and the makers of their machines) and fitting two rolls onto a standard truck bed.

     Absolutely nothing to do with the ergonomics of reading.

   • The practice of splitting newspaper stories into narrow vertical columns, was because it was convenient for the typesetters; and it allowed the page layout to be 'reflowed' to accommodate breaking news, late arriving pictures or edits to the story.

     Absolutely nothing to do with the ergonomics of reading.

   • A-series (A0/A1/A2/A3/A4/A5). The standardisation of a 1:√2 ratio and 1m² A0, and subdivisions thereof.

     Absolutely nothing to do with the ergonomics of reading.

   • B-series. The geometric means of the A-series sizes. Ie. B1 is half way between A0 and A1 in area.

     Absolutely nothing to do with the ergonomics of reading.

   • Inch sizes. Based on archaic sizes and how many times they were folded/cut. Sizes probably originate from what size rectange could be cut from the animal that provided the skin. (Calf for vellum etc.)

     Absolutely nothing to do with the ergonomics of reading.

   The upshot is that paper sizes and paper media practices came about for the convenience of the construction of the media, not for the convenience of the reader; and as such should not be used or referenced in the design and development of VDUs or screen-based user interfaces.

   That perpetuating paper media practices that originated, because you got a certain size & shape rectangle when you cut the legs off an animal skin, just makes no sense.

Its what makes the PDF format such a joke, despite that I have literally hundreds of the damn thing on my machine.