Back in the days of film photography, you had to think very carefully about the aspect ratio of your image before you shot it, and different aspect ratios held enthusiastic fans that specialized in their usage. The advent of digital and the standardization of the sensor into just two aspect ratios has seen that focus die away a bit, but they remain highly important in how your images are rendered, and this excellent video tutorial discusses their usage.
[ Read More ](Originally posted by Alex Cooke)