Quote Originally Posted by tkamiya View Post
If you set the double slit in such a way a single photon can pass both of them AND interfere with each other, then p+p and p-p will take place at the image plane. That would mean the image will have an alternating strip of doubly exposed area and no exposure what so ever.

BUT... if this is an optical system involving one or more lenses, it may be far more complex than that. I would imagine if the slit is placed in image forming plane (there are multiple of these in a complex lens system) or elsewhere, the result will likely vary.

If it is at an image forming plane, you might actually get a image with only visible part being where two slits are.

You cheated first by amending the original setup!
But the main point here is observed with film, or not observed.