The surrealism depicts lanscapes, situations born in the imagination of the author. They are behind the reality. The surrealsim was born with the photography, and the first elaborations where made in the 19th century. Here above we see an example of solarisation. It was made on a picture I made in the early years 7s in Bruges, Belgium, then elaborated in darkroom. For the technique of solarisation you can follow the link to Wikipedia.
After This kind of elaboration surrealism began with mounting, always in darkroom, more images for creating a new one. This technique was called photo montage and this is the technique used nowadays for making surreal picures, using the computer instead of the darkroom. But I can say that the difficulty for making a picure like this here above made in Belgium was very high!
Surrealism is well known and it is possible to find also pictures with even Salvador D’Alì involved with photographers in creating this kind of artworks. In the surrealism the images are not changed, but create a mosaic for a new image.
We can say that now surrealism evolved itself into photography based digital art, this is because the new technologies changed its analogic origin.