This post was inspired by a discussion on the forums of the photography website dpreview.com
People just begining to study photography will quickly be introduced to the idea of the "rule of thirds". The rule looks somewhat like a hashtag or tic tac toe pattern but more evenly distrubuted across your frame. If you have a rectangle (including a square) you would create this pattern by drawing two horizontal and two vertical lines spaced evenly through your frame creating nine boxes.
The rule says you should place the important parts of your image within your frame so that they fall on either a line or a point of intersection. The point of all that is to help you create a more interesting and balanced looking image than you would get if you had your subject right in the middle of your photo (or painting). There are other compositional ideas meant to achieve the same goal and most of these have been studied by artists and mathematicians for millennia.
Photography is a much more accessible art form in our time than drawing or painting. Creating a decent (not necessarily good or great) photograph is usually much faster and easier than creating even a mediocre drawing or painting and requires less practice then many more traditional forms of art. This has both advantages and disadvantages. One advantage is that its accessability helps draw more people into the world of art, both in appreciation and creation. This can act as a disadvantage as well. Due to the advances in modern camera technology it's possible for most all cameras, including those in mobile phones) to capture a decent acceptably exposed image by doing nothing more than pointing your camera and pushing a button. This can lead beginner photographers to bypass the type and depth of study that artists of more archaic art forms practice. This brings us back to the rule of thirds and other forms of composition.
There are many other compositional guides besides the rule of thirds, too many to discuss in this post. A lot of people look at the topic backwards. They try to figure out what the best compositional rule is and try to fit their subject to that rule rather then thinking about what message they want to convey or emotion they want to evoke, then what subject or subjects will help tell that and finally how can I compose, light, color, and position all of that to fulfill that goal. People also tend to forget that the compositional guides or "rules' are meant to assist with the image as a whole, not a single subject. All of the individual elements should be considered as to how they are balancing in the image. If you are taking a portrait that might mean how the collar of a shirt appears, how the arms and hands are placed, or where an environmental element such as a lamp, chair, or clock is placed. It might just be where a patch of light falls. Sometimes these elements are placed in ways to create harmony and other times to create a feeling of discord or unbalance. The compositional guides can help with either purpose and your intent needs to be the thing that determines it, not the rule. -- Juxtaposepictures.com Instagram/juxtaposepictures