It isn't. For example, you probably think that the photo below is a photo montage, created from several different individual photos.
[This Mind Bending, Colorful Photo Mosaic is Actually a Single Photograph singlephotograph] It's not: http://petapixel.com/2013/06/20/this-mind-bending-colorful-photo-mosaic-\ is-actually-a-single-photograph/ <http://petapixel.com/2013/06/20/this-mind-bending-colorful-photo-mosaic\ -is-actually-a-single-photograph/>
