The horizon line is where the sky meets the ground. Or as the dictionary says it: the line at which the earth’s surface and the sky appear to meet.
The big question you should ask, and see if it works for you is: Does the rule of thirds apply to the horizon? And if so, how?
The Rule of Thirds is the process of dividing an image into thirds, using two horizontal and two vertical lines. This imaginary grid yields nine parts with four intersection points. When you position the most important elements of your image at these intersection points, you produce a much more natural image.
So, what would happen if you put the horizon on the line of the grid? You are right, you would get a more pleasing photo. Here’s some examples:
Now with this, you can make your choice you want to do with the placement of the horizon, but, don’t put the horizon right in the middle. There is something telling in either the top half or the bottom half of photos. Use it.
Adam Williams explained it this way:
In the first example, we have roughly two-thirds foreground to one-third sky. This composition tends to accentuate depth in our photos, as the viewer can take the journey from the close details in the foreground all the way back to the main subject, Uluru.
In the second example, the ratios are reversed: we now have roughly two-thirds sky to one-third foreground. With more sky, this composition tends to communicate a sense of open space, while still allowing our viewer to journey from front to back.
To use the placement of your horizon, make sure the horizon line is in one of the “rule of thirds” line. Can you break the rules? Of course, but, beware it might only be you that likes it, so, pick which one is the best.
Here are just a couple of more horizon photos using the rule of thirds: