A pinhole camera has no lens. The effect here is like a pinhole camera, but a pinhole camera is nothing at all like a lens. Pinholes diffract light. Lens refract light.

EDIT: Of course you can't resolve an image through diffraction. That's not how pinholes cameras work. Diffraction negatively impacts image resolution, but it absolutely happens when light passes through them. But, although lens do use refraction to resolve an image, that same process also has unintended negative effects on image resolution (spherical aberration, chromatic aberration, etc.). I didn't bring up any of that because it was ultimately a distraction from the important part: narrow gaps diffract light, lens refract light, and pinhole cameras do not work like lens.

Our window blinds at school had tiny holes in them for the strings to go through and they had the exact same effect. You could see the eclipse projected once the tables.

Additionally, if you can make sunlight shine through a tiny hole that is somewhat level with the ground into a dark room or box, onto a flat, white surface, you can often see a projection of the world outside if the sun is hitting everything just right, the image will be upside-down and reversed, but often in full color like a video image.

Naturally occuring camera obscura must have freaked people the fuck out in olden times.

The ratio of the size of the image to the distance from the pinhole is the same as the ratio of the size of the sun to the distance to the sun.

Only if you know the sun's size, which kind of presupposes you know its distance.

how?