Multiple exposures
When I try to make a nice multiple exposure, I usually screw it up. Because I think too much what fits on the previous image.
It also happens that I totally forget that I wanted to make a multiple exposure picture and just shoot without advancing the film. Mostly, the result is much better than when I think about the image, the framing, …
Like, this picture for example, I was quite excited about seeing the zeppelin right in front of me that I totally forgot to advance the film in my Diana. So when it got developed I was quite surprised to see there were multiple zeppelins on the picture. And actually, I think that it turned out pretty good.

