Landscape vs Portrait

[Nick]

I'll use the 15C in a variety of ways:

On a desk:

• I prefer to set the calculator on a notebook. Or second to that, I'll use the case or something else for grip and stability. In a pinch, I'll pinch it with my left hand thumb and index while it's on the desk.
• On a desk, I'll either 1-finger the keys with my right index or I'll use the 4 fingers of my right hand to 'type' across the entire width of the device, freeing my left hand to index the work.
  

Handheld:

• My natural hold is the 2-thumb method, and yes the left thumb doesn't do as much work unless you're doing work on something like the 12C or debugging a 15C program.
• I'll also hold it in my left hand.. imagine thumb on the left side of the unit with middle finger on the right hand side, with the other fingers securing it across the length of the palm. In this position I can 1-finger press or 4-finger type (sort of like a wrist-worn keyboard inside your palm). This is useful when you have documents in your lap or leaning against a desk.
  

The 15C is my favorite all-around calculator. <3

If you preferred a portrait format, the 34C would be its predecessor at a cost of battery life -- hours vs years/decades, but I find the landscape format to be more ergonomic. Being shorter vertically lets you set it on top of the work. The golden aspect ratio is a plus.

By comparison, the 15C has 40 keys, 2 shift keys, with the only non-facing functions 10 of the 12 tests and 10 of the matrix operations. The 34C has 30 keys, 3 shift keys, and lacks the side-by-side complex stack and matrix functions.

Ergonomically, the landscape format avoids the up/down motion strain -- there's little to "reach up" for. The natural world is landscape... we look side to side, work side to side... that influenced the trend in wider displays rather than stacking them. As a test, look forward -- move your eyes left to right then allow your head to join, scanning left to right. Now look forward again. Look up with your eyes then down, then allow your head to join.

I consider the format much more than a gimmick -- there's been a few articles on the choice of layout in the design. The 12C (also in the Voyager line) is the most fluent TVM calculator I know in terms of both the number key presses to run the formula and the speed of 2-thumbing between function and data entry. I carry them together as a set. The landscape format lets both calculators fit vertically on a desk, nearly square.

Yip,
Nick