Or take this image:
That is a black-and-white photo with some colored lines laid on top, but you perceive colored clothes, colored seats, etc. If you look closely at any one small part, you will correctly note the gray image and the colored lines, but everything outside your fovea's range is a blur, so your brain mashes it all together.Â
The tiny size of the fovea is also responsible for a lot of classic optical illusions. There's some debate among eye scientists about precisely why it is that you see imaginary gray circles in the intersections of this grid:
But you sure don't see any in the specific intersection you're focusing on. The fovea perceives that one correctly; everything else is deduction based on a blur. And you’ll swear that the following is a GIF, and moving: