Level Horizon
Because we humans are quite adept at standing upright, the way we view the world tends to be on the ‘level’. As a consequence, as soon as we view something which appears otherwise it just doesn’t sit comfortably. Rather than go to all efforts to level the horizon I believe the trick is in making the horizon ‘look’ level. To explain this let me invoke my DIY tendencies. Let’s imaging you want to put up a frieze in your child’s bedroom, the stalwarts would tell you that it has to be absolutely level. The problem comes in realising that no room is built absolutely square, level and plumb. As a result your perfectly level frieze will highlight the fact that your ceiling is NOT level and it will look awful. The key is to make things ‘look’ level. In the example above you would simply make sure the frieze was parallel with the ceiling, even if the ceiling was way off the level. Anyway back to photography and in the absence of a perfectly straight horizon (which is only likely to occur at sea) look to other things as a guide. Trees and plants tend to grow vertically upwards and an image will look odd if these are at an angle. Also buildings must always be vertical. Should none of these points of reference exist in your image you are free to choose what ever feels good for you since those viewing your image will also have no point of reference.
A good level horizon. Since we are looking at the sea here, it would immediately become obvious if the horizon was not level.
In the absence of anything else, use a tree. People expect trees to grow vertically upwards. Anything vertical will do; a building, lamp post etc.
With no points of reference at all do what you want since no one will be able to tell the difference anyway!

Andy Harbin Photography, Stroud, Gloucestershire. UK
2010 © Andy Harbin. All rights reserved.