Okay I do have a clue what it is and well I don't think you'll ever guess it really. I got a hold of some very damaged negatives, they were unusable, they had patches of all kinds of colours on them and they couldn't be used for printing. But just the colours themselves, on the negatives, were really pretty. I got an idea...maybe I could use the damaged negatives as some sort of purple filter. I didn't really think it would work but it was worth a try. After a lot of fumbling about I managed to bluetac it around a standard lense and I was planning to take a bright daylight photo, hoping enough light would find its way through the "filter". But I discovered - woops - the sun had already set. So I pointed the camera at my nightlight (not exactly a brilliant lightsource but it was all I had) and took a photo...I knew it would be underexposed and I didn't really think it would be anything at all so imagine my surprise... So this not quite a photo of a negative, and not quite a photo taken through a negative. :-)