[vlachen]

I did it back enough in the day that I used a negative from getting pictures developed. I think I got the idea in Hardware Hacking Projects.

[atahanacar]

I did the same too, but funnily enough I stumbled upon it by accident when I was trying to find things that pass IR through but not visible light (like coke, sunglasses, ink etc.) using my Sony camera with nightvision mode. I was on a quest to get "x-ray vision".