Artist Reaction

As a photographer and someone who uses photoshop often I am quite fascinated by the works of these artists. I must admit that I have not been exposed to too much digital art, especially images that have been not only manipulated beautifully but set up in such a great way. I am curious how Jeff Wall and Gregory Crewdson achieved the images that they did through photoshop and would love to see the picture that the image originated from so I can see how dramatic of a change it was.