I’ve made some simple pictures with a single-coloured shape on a single-coloured background. Or sometimes I’ve used a grid of dots. If the background is lighter than the shapes, I can see ghost-like versions of them that are the same colour as the background, except lighter - even if the background colour is white. When I move my eyes around, these ghost images move around. When the background colour is darker than the shapes then the ghost shapes are even darker than the background colour - even if the background colour is black.
I was wondering what that effect is called so that I can do more research on it. I don’t understand why the “ghost” image (what is it called?) is even lighter or darker than the rest of the picture.
I’ve seen pictures which show the path that our eye takes when it is viewing a picture - a jagged line which shows where it has focused on. I was wondering what equipment they use to track eye movement.