Law of the horizon
The law of horizon says, simply, that the picture must be drawn two imaginary horizontal lines (either vertical or horizontal format) that will divide the picture into 3 equal parts.
The main object or subject of the photo should take about 2 bands and the remaining 1 band. This of course is variable and will depend on the importance of each area.
This rule is not used only when there is a horizon line but any more or less horizontal line that is strong enough and marked to divide the picture into 2 spaces.
If we have a photo that is generally horizon we have to avoid putting the line in the middle. Will give the feeling that the picture is cut in half.
In this photo you can see the horizon, though not see whole picture divided in half. The result is that the background model and compete in importance and the viewer ends up not knowing that is what is wanted to show.
In this picture (above photo is that was cut with Photoshop as an example), the viewer has no doubt that the most important in the photo is the model. The horizon line is above and the model comes to occupy more than 2/3 of the photo.
This is another example where the main subject occupies 2/3 of the image and the bottom just a third (approximately). And here there is no doubt that's the important thing in the picture. Also there is nothing to distract the attention of the main subject.
