I compose an image based on an aspect ratio, the ratio of width to height (w:h), that works best for my composition. Most of my images are shot in landscape mode where the width of the image is greater than the height of the image. But I will often shoot in portrait mode – height greater than width. I work from a basic set of aspect ratios, which are outlined below and are expressed in landscape mode, but could also be shot in portrait mode.
Full-framed (3:2): this is my most common aspect ratio and is the standard frame-size of most full-frame DSLR cameras, which are my cameras of choice. It is a pleasing and somewhat dynamic aspect ratio. Most common image sizes (inches) are 8×12, 10×15, and 12×18.
Micro Four Thirds (4:3): this aspect ratio is found on many “mirror-less” cameras, especially cameras with a sensor that is less than full-frame.
Square (1:1): a classic format with medium format cameras. It is not as common these days, but with certain images it can have a powerful impact.
Cinematic (16:9): this is a widescreen video format that can improve the composition of many images, where there is too much “dead” space in the sky or the foreground.
Golden Section (1.618:1): this is nature’s aspect ratio. Many naturally occurring objects conform to the Golden Section. It can be useful as a bridge between a full-framed and a cinematic aspect ratio, when neither is quite right for the composition.
Root 4 (2:1): a classic panoramic aspect ratio.
Double Golden Section (3.236:1): this is a wide-span panorama that leverages the Golden Section.