Emphasis
It works by directing your focus to a specific key point of the piece of artwork. Artists use things like Contrast, Isolation, Location, Convergence, and the Unusual, to emphasize a specific part of the picture and draw your attention to it.
Contrast
The picture above shows a yellow fish with a grayscale background. Notice how you automatically draw your eyes towards the fish, this is called a focal point. This specific aspect of emphasis you are seeing is known as contrast. Contrast is an example of emphasis, it is when your eyes are drawn to a focal point due to things like: color, shape, and size.
Isolation
Artists emphasize things with Isolation. They accomplish this by taking an object of interest and placing it apart from other things in the picture. In this picture, the woman is isolated from other objects in the painting, in this case, the house. The way the artist achieves this is by making the house small, and placing it in the background. This makes the house look far away, which places your attention on the woman, who is the biggest and closest thing in the large field. There is more than one object, but one is more emphasized because it is isolated from the other.
Location
Artists use the element of location in emphasis to pull your attention to a focal point. They usually do this by placing the most interesting or detailed part of the creation in the center or slightly off center. In the picture above, notice how the shore is just above the center of the image. This is the first thing you see, and then you notice the surrounding details such as the wooden railing and plants.
Unusual
In this picture, the unusual is displayed by a giant thumb in the middle of a street, where its surroundings seem normal, making it stand out. Unusual emphasis art is when one thing stands out in a picture because it is an oddity in its normal surroundings.
Convergence
The picture above shows Convergence, because all the ridges of the plant's leaf point straight to the opening/center of the leaf (also known as a focal point). This aspect of emphasis is created when things in the artwork point to the main focus of the piece( focal point).