> Is there any difference between taking a 1000 year exposure and taking a photo every day for 1000 years and laying them ontop of eachother? There is a differ

> Is there any difference between taking a 1000 year exposure and taking a photo every day for 1000 years and laying them ontop of eachother? There is a difference between taking a photo every day for 1000 years, what you end up with is, say, a 365,000 second exposure. This is an actual 1000 year exposure. The algorithm where you take 60 1/60th second exposures over the course of a second and then stitch them together is popular. There are many mobile apps that do this and try to use edge detection / "AI" to make them line up, so you can take handheld long exposure shots. (Spectre is an iOS app, but I'm sure there are others.) You can also do it yourself with a tripod and photoshop. The results are good, and it lets you take long exposures when you are constrained by having too much light and no ND filter / tiny aperture on your lens / etc. > Wouldn't it produce a solid white image after a single day? In general, reciprocity holds in photography. A 1 second exposure at f/8 is the same as a 2 second exposure at f/16 given the same sensor. (Films have a technical limitation called "reciprocity failure" for long exposures. Silver halide requires TWO photons to hit each atom, and the statistics of that aren't linear. This means that film exposures depend both on the shutter speed and ISO sensitivity; a properly exposed long exposure on film will often be longer than what the math dictates. The box that your film comes in will often give you a number to multiply your calculated exposure by.) So what they need is exceedingly low ISO film. A picture of a sunny scene would generally be exposed at f/16 and 1/<the ISO of the film>. A pinhole lens can't open that wide, they're more like f/180. That is "7 stops" less light than f/16, so would need a shutter speed of 1.3 seconds to capture the same image. Now you can see how insensitive the "film" in this camera is; it needs 31,536,000,000 seconds of exposure. That means it's 3.17e-11 ISO film they have in there. What quantum effects happen to film that insensitive, I don't know. They say it's paint fading, and I don't know what the rate is. It might end up being overexposed. (Film is usually OK being severely overexposed, the opposite of digital. No idea if paint fading behaves the same way as silver halide. Probably!) One other thing to think about; films often have differing sensitivity to different colors of light. Early film was overly sensitive to UV light, because it contains so much more energy than red light. Modern black and white film is pretty linear over the colors of light, so you end up with a picture that looks right to your eye. Paint does not have this carefully-designed chemistry, and is probably only sensitive to UV light, so that reduces the effective ISO of this camera setup even further. It won't respond to light you can see, only UV light. But, that works well enough to yield a recognizable image. (The problem in photography is that the sky contains too much UV, and you end up with an ugly white contrast-less sky. In this case, I don't think they care.)