A merger in photography occurs when a background object is directly in front or behind a subject. If there are multiple subjects in the photograph, a merger can also occur if both main subjects overlap with each other or touch the sides of the picture frame.
A merger can cause the background object to distract from the main focus of the picture or otherwise ruin a perfect photo shot. An example of merger in photography is a tree growing out of a subject's head due to a bad angle. To avoid mergers, photographers should pay attention to the whole frame and adjust angles when necessary.