Diagonal lines are easily created in photography but occur less often naturally than horizontal and vertical lines. They can give a feeling of depth and unlike the lines running parallel to the image frame, they give a sense of movement and direction. Diagonal lines can feel unstable or give a sense of falling. The images below are intended to demonstrate these attributes of diagonal lines.
The diagonal in this image has been contrived by being positioned to the side of the boat moving towards the came and then to further emphasise it, the camera has been slightly rotated. This image is using the diagonal to convey a sense of direction.
This image is using the diagonal to emphasise the depth of the bridge. The top of the bridge naturally draws the eye but looking at the uprights, it can be seen that they are getting progressively smaller, forming additional diagonals in the image.
Another demonstration of how diagonals can be created by using perspective – this time without using any camera rotation.
This last image is creating diagonals by making use of converging lines.