Finished painting, and a note on painting sizes
Finished product. This painting is teeny tiny.
I was doing some reading on standard painting sizes and remembered that in France they not only sell canvases based on size, but also on rectangular shape. For this they use three basic ratios expressing how many times the smaller dimension goes into the larger. Sometime in the 1800s, the French split these three ratios into categories: Figure (~1.3 ratio), Landscape (~1.5), and Marine (~1.8). Making sense of these numbers is easy when you think that 1.0 is a square (because every side is equal and so they go into each other exactly once), so the farther away from that you get, the longer the rectangle.
So if you want a canvas that is 18cm in length, you must then decide if you want:
a squat rectangle, whose shorter side is about 80% of the longer (14cm)
a pretty standard rectangle, whose shorter side is about 65% the longer (12cm)
a long rectangle, approaching 50% of the longer (10cm).
Each size increment has a number (0-120), so you could go in the store and ask for a "size 8 marine", and they would know exactly what you want. The table below is useful in laying out all of the options. Of course, outside of France, art suppliers often already produce canvas sizes using this system. I just haven't come across any distributors selling them in that fashion.
For my paintings, I'm pretty loyal to the 1.5 ratio that I photograph in (3888 x 2592 pixels), putting me at Landscape. However, this last painting was 5" x 7" with a ratio of 1.4, meaning more of a Figure ratio than I'm used to. This ended up working out nicely -- I find that vertically oriented paintings can easily seem too tall and elongated (whereas extra length in a horizontally oriented painting creates more of an expansive, panoramic feeling) so the slightly more concise ratio eliminated any distracting and unnecessary height.
I just stretched two other frames, one at 13" x 19" (landscape), the other 15" x 27" (marine). The second will be exciting not just because it is more than half a foot bigger than any paintings I've done in the last couple of years (and when your paintings are as small as mine, half a foot is a lot), but it will also be a much longer composition. It makes me think of letter boxing in film, and the difference between full screen and wide screen (though not quite as abrupt a shift).
And to think I've always turned my nose up at math!