Exercise: Vertical and Horizontal Frames
Take 20 photographs in vertical (portrait) format and 20 photographs in horizontal (landscape) format. Attempt to ensure that both formats are of the same scene. Compare the ‘pairs’ of images and note that each scene can be fitted into both formats fairly successfully, but some scenes suit one format better and format selection is really mostly a matter of a habit.
I found this exercise quite easy to complete without thinking about the orientation of the viewfinder and looking for images that fitted the vertical (portrait) format better.
I also would not agree that the choice of orientation is just a matter of habit. Although the image required can be obtained from both vertical and horizontal (landscape) format, the fact is that the perspective changes as does the need to crop images to make them the same. By having to crop, the section of the image required has to magnify and the sharpness could therefore become compromised. By using the most suitable orientation for the photograph being taken reduces the necessity for large amounts of cropping and possible sharpness compromise.
My observation from this exercise is that where a major element of the image required is tall by comparison to the rest, then vertical (portrait) orientation is best. Where this condition is not met, then horizontal (landscape) orientation is better.
I have chosen the images which I think show this most clearly: –