Whenever I look through the waist-level viewfinder on my Mamiya 645 medium format SLR, I have this immense feeling of depth. Almost as if the image was 3D.

Then one day I started squinting my eyes. Left, right, left, right, .. and I noticed that in fact each eye sees a slightly different picture.

TWO DIFFERENT IMAGES.

THROUGH ONE LENS.

ON A SCREEN.

That's kind of the definition of 3D vision right there. Implemented in a 30 year old camera.

My best guess for an explanation is that instead of being a point, the lens is a surface, and thus light can travel through it in different paths. How the different paths reach the different eyes is a different question.

I see you shake your head in disbelief... let me convince you with this video I just made


Can you explain what's going on here?