The eye is very sensitive to imbalance and even though the horizon, or vertical lines might be only slightly out, the eye can pick still pick it up. Fortunately on many camera viewfinders there are lines to help get the horizontals and verticals right, but sometimes things go astray anyway even though we are sure everything was square when we took the picture. Not to worry though, because even the basic on line photo editing usually allows you to correct sloping horizons or wonky walls.
I liked these in black and white.
Keep it on the level!
Derelict Crane on Dublin Harbour Breakwater - geometrical shapes will be a give away for wonky horizons!
When I am doing landscapes, and have my trusty tripod with me, I use the inbuilt spirit level to get things as horizontal as possible. I also have a small cube level which my son gave to me one Christmas to fit into the 'hotshoe' on top of my camera. This is really useful when I am doing panoramas and stitching multiple images together. If I had not got the pictures straight using the level I would have probably lost parts of the picture at the top and bottom when the software stuck the images together.
The Harp Bridge and the Jeanie Johnson tall ship on the Liffey
Sometimes you may want to deliberately tilt the camera over to create energy and abstraction in your image. That is great if meant! I have blogged on that before if you want to search for it.
The swing bridge that does swing! Looking upstream into Dublin
Keep it on the level!