pinhole cameras

Yesterday was my first multimedia lesson and we created pinhole cameras from beer cans. I did this last year, during my foundation art and design course at college, but we used a flatter surface (I think it was a biscuit tin, but I suppose it's alot easier for a bunch of students to get hold of a beer can, rather than a biscuit tin...), this time things didn't work out so well. The images were often under/over-exposed, however, I thought the curved images created from the rounded shape of the can, were far more interesting than a flat image, just not as practical.