The aspect ratio of a painting is the relationship between the height and width of the finished piece. In painting the most common aspect ratio has been 3:4.
This means that for every 3 inches in the horizontal/vertical, there would be 4 inches in the other direction. An example would be a 30” by 40” painting. By reducing the size but maintaining the same 3:4 aspect ratio relationship you would have an18x24”, 12×16” or a 9×12” painting.
The aspect ratio remains the same regardless of whether an art work is hung in a horizontal or vertical direction.
This 4:3 aspect ratio is visually comfortable for most viewers and replicates the standard television format that was used until recently. With the advent of HD TV, the standards have changed to a longer screen and a 16:9 ratio is now the flat screen TV norm. This changes the shape or aspect ratio of the rectangle that is viewed by most people on a regular basis.
This change in aspect ratio is also reflected in digital photography and in paintings. This new TV standard has increased the popularity of the longer 2:3 ratio. The new sizes in paintings would represent: 8×12”, 12×18”, 16×24”, 20×30”, 24×36”, 28×42” and 30×45”.
Framers use these standard sizes for many of their ready-made frames which is a cost saving to the Art Collector.
I create all my paintings in standard sizes so custom framing is not necessary