These photos are really great. I love working with light and shadow to create sort of surreal environments. The tutorial was on long exposure photography with absolutely no light. These images almost remind me of HDRI's. Here are some examples of Long exposure photography without lights.
I want to take out a tripod sometime and try to create some images similar to ones above. I would suspect they used a high aperture rating like f/22 or f/32 with a shutter speed of maybe around a minute or two. This is the tutorial that i saw.