Dark-frame subtraction

Okay, so imagine you're a photographer taking pictures. Sometimes when you take a picture, there might be some extra junk in the picture that you don't want. This junk can come from things like the camera itself, or from the environment you're taking pictures in.

One way to get rid of this junk is to take a second picture with the lens cap on. This second picture is called a dark frame, because it's just a picture of darkness. But even though it might not look like much, the dark frame helps us get rid of the junk.

So what we do is we take our original picture and we subtract the dark frame from it. We do this pixel by pixel, which means we compare every single pixel in the two pictures.

If a pixel is the same in both pictures, we know that it's not junk. But if a pixel is different in the dark frame than it is in our original picture, we know that the difference must be junk. So we subtract the dark frame value from the original picture value to get rid of the junk.

Overall, dark-frame subtraction helps us make our pictures look better by getting rid of unwanted junk. It's like taking out the trash!