Photography 101: Prolonged Exposure

A prolonged (or extended) exposure is responsible for a large percentage of "ghost" photographs.

Behind the camera's lens there is a part called the iris. It works in a similar way to the human eye, allowing light into the camera where it is recorded on film. In most modern photography, this action takes place in a fraction of a second, and the camera records what it "saw" in that fraction of a second. resulting in a photograph like this one:

This photo was taken in 1/200th of a second. Which means the iris was open for only 1/200th of a second. Pretty quick. I had to use a flash, because I was in a dark room and there wasn't enough light to illuminate the object in that short a period of time. You can tell that I used a flash, because the flash reflects off the shiny surfaces of the figurine and the knob of the washing machine.

In the next photo I did not use a flash. I was in the same dark room, but instead I prolonged the exposure time. Instead of a fraction of a second, I left the iris open for a full 32 seconds. Also, at 15 seconds, I removed the figurine. See what happened:
It's transparent.

That's because the camera, in it's 30 second exposure, captured 15 seconds of the figurine, and when I removed the figurine, it captured 15 seconds of what was originally being blocked by the figurine. Also notice that there is no flash reflection.

Many ghost photographs are victims of this quirk of photography for instance, in this famous ghost photo:
We see the priest (or whoever) kneeling in front of the ornate altar. it's indoors and the ambient light would not been enough to illuminate the room for a photograph. The photographer would have had to use a flash to illuminate this scene, but there are no signs of flash here. We don't see reflections of flash off the shiny surfaces.

The only other way to have illuminated the room would be to use the extended exposure, and that's just what the photographer has done. This is evidenced by the brightness of the candles along the side of the photo, as well as the brightness of the light coming in the window above the altar. The longer the camera's iris is open, the brighter any light source in the photo, now matter how dim to the human eye, is going to be.

Now all we need is a kneeling person who is only there for a short time and a prolonged exposure shot will create the photo we see here.

Don't believe it just because someone said it was real, use your own judgement.