"If I hold that board up sort of perpendicular to the sun - no matter what the shape of the hole - I still get a round image of the sun, because the sun is round. And so the image is going to be round, too.
"And if it's a small hole or a bigger hole, all the images are the same size, and as you move back, they all get larger. The image gets bigger the farther back you move because the light diverges more. But it also gets dimmer, because no matter where you put the board, you still have the same amount of light coming through the hole. It's just spread out more.