Original Definition Photomontage is the process and the result of
making a composite photograph by cutting,gluing,
rearranging and overlapping two or more photographs into a new image. Sometimes
the resulting composite image was photographed so that a final image appeared
as a seamless photographic print. Here are two examples from around 1857 -
Fading away by Henry Peach Robinson and The Two Ways of Life by Oscar Reilander
Now done through image-editing software, referred to by
professionals as "compositing", and in casual usage is often called "photoshopping",
due to the software often used. Commonly used in Graphic Art and Professional
Photographers' Studios to produce book covers, film posters etc or to generate
interesting family or wedding portfolios.
Multiple images taken at the same point and then combined with layer masks etc
Using special software eg Andrea Mosaic where you can upload an image and give the software access to your image library and it will create your chosen image using tiny versions of your library images. Link http://www.andreaplanet.com/andreamosaic/
Montage of person on background very popular with some in the amateur photographic circles and hated by others - your choice - certainly some work better than others
Sometimes images that appear composites are not as in the case of Ian Munro's images
Copying Ideas or Plagiarism - a narrow gap
What to do about it?? - some competitions now require RAW files to be submitted before acceptance as in the Wildlife Photographer of the Year