What causes the “ghosting” effect in photography


I’ve seen this a lot in action shots but I’ve never gotten a good explanation

[example photo](https://twitter.com/heat1995viewer/status/1621152303729475585?s=46&t=Ask-Z_AY7uucFNoW6Vc7FA)

In: 5

Hey kiddo,
Imagine you have a drawing board and a big white paper! You want to draw a house on it. You draw your house in like 5 minutes, then you go out to pee cause you drank too much Mountain Dew. You come back, and you realize that the skateboarding kid from the block you hate, ran into your room and quickly scribbled himself on your drawing.

Now, the house is the original photo made in low light with a longer exposure, the paper is the sensor in your camera and the scribble of the skater is a result of a flash going off on the guy who jumped into the photo in the last minute.

Two things:

1. You take a picture of something that does not move. Then you take a picture of that same thing from exactly the same position with another object in the picture. You superimpose the two images, and the object that is in one picture only will look transparent against the object that is there in both photos.
2. This used a similar technique but is also Photoshopped. You can tell because some parts of the skateboarder are transparent and some are not. If this was a simple superimposed image, all parts of the skateboarder would be equally transparent.

The shutter has to stay open for a longer period of time in low light. The background is solid because it is in frame the entire time that the shutter is open, but the main subject passes by quickly and doesn’t allow the camera to get enough light reflected from them to make them appear full, which makes it appear as a ghost.

This is called a [multiple exposure](https://en.wikipedia.org/wiki/Multiple_exposure), or double exposure if it’s just two images.

Hey OP, unfortunately no one has actually answered this correctly. This is a long exposure and a flash/light is used to provide a lot of light on the subject for an instance.

ELI5: Cameras take photos by allowing light in, and a slower shutter speed will allow for more light to be captured. This is especially helpful during the night as it will need to “absorb” more light in. While the skateboarder is moving in the dark, there isn’t enough light reaching the camera to show up in the final photo, in comparison with the rest of the scene. For a small moment, a flash or bright light is used, which lights up the skateboarder and ultimately reaches the camera. This results in the “ghosting”, as the camera sees both a really bright skateboarder for an instant, but also the darker background for a long time.