The rule of thirds is arguably the best known among the pictorial composition guidelines. Indeed it is one of the first rules of composition most people pick-up while learning photography.

The reason why rule of thirds is widely applied in photography is the way it helps in placing the main subjects or the points of interest at the most effective positions in the frame.

For a recap, here’s what the rule of thirds is about. The frame has to be divided into 9 equal parts using four lines that divide the frame into vertical and horizontal thirds.  The rule of thirds suggests that the most interesting elements of the composition should be placed on or nearby the four intersection points of these four lines.

It has been suggested through research that if the point of interest is placed along these intersection points, the viewer can interact most effectively with it, than if it were placed at other areas, including the centre of the image.

While shooting portraits, the rule of thirds guides us as to where to place the eyes, or face or the most striking features of the portrait to make the most impact.

The rule of thirds also guides us about where to place the horizon in a landscape image. The general guideline is to keep the horizon along one of the horizontal lines, so as not to cut the frame in the middle.

Whether you want to use the top line or the bottom one depends on which part of the scene is more interesting, for example, if the sky looks more appealing than the foreground, it makes sense to give it more space 2/3rd and keep the horizon at the lower 1/3rd line. If the foreground is more interesting, it makes sense to do the reverse.

Rule of thirds also helps you when you’re deciding to give lead space to moving subjects or subjects looking towards a certain direction like the left or the right of the frame.

Of course, if you practice enough, you will be able to imagine these lines, and place the points of interest accordingly. But in case you like to be accurate and sure, Nikon DSLRs and Mirror less cameras offer a setting which makes these lines actually appear inside the viewfinder.

These lines will also appear on the LCD monitor in live view mode. This is very useful while shooting videos.

The rule of thirds is also applicable while editing your images in post-production. While cropping an image using Nikon software like View NX-i or Capture NX-D, you are shown gridlines similar to the ones seen in the viewfinder, to help you place your main subject or its point of interest in the most effective position. This can turn unimpressive images into more effective ones. 

Of course, photography is an art form, and that leaves plenty of room for experiment. The rule of thirds is ultimately a guideline and there will be many occasions when you will find the rule can be broken to get what you want. So, follow the rule generally, but follow your heart at times too!