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I learned that a pinhole camera inverts the image on the film strip:
Is it to possible to test if the image gets inverted without the film strip on which the image is projected?
For example: I made a small hole in the cardboard and tried looking through it, but the image didn't appear inverted to my eye. Why?
Is there a simple experiment I can use to prove that the image gets inverted without using a filmstrip?
Replace the back wall of the camera with a sheet of tracing paper, ground glass (or similar translucent material) and observe the resolved image from behind the camera. You may need a dark sheet over your head (and the rear of the camera) to allow the dim image to be visible. This should remind you of how very old cameras were operated (for exactly the same reason).
It may also be worth looking up camera obscura to see more examples (at different scales) of the principal in action.
Pin-hole cameras, camera obscuras, cameras and the human eye all resolve an upside down image - which is then rotated for viewing (or when being interpreted by the brain).
Make a simple, non-photographic pin-hole camera. Start with a cardboard tube. The round Quaker Oats breakfast box is perfect for this job. You can use any cardboard mailing tube. Cut off both ends, now you have a just the tube. Cover one end with a single sheet of tracing paper. In my day, we called this paper “onion skin”. Cover the other end with aluminum foil. Use duct tape to affix the foil and the tracing paper. Using an sewing needle, pierce a tiny hole in center of the aluminum foil.
Now darken the room as best you can. Allow your newly constructed camera obscura to look out a window. You will see an upside down image of the outside world projected on the tracing paper.
The camera obscura, as it was called, was popular in Europe before the camera. Artist made and purchased elaborate camera obscura devices. These were often placed inside a tent. The idea was to use the projected image as an aid, they traced the image and later, finished it using water colors or oils.
How did you look through the pinhole?
If you put it far from your eye you have seen nothing. It is small hole and you have seen one "overexposed" point behind dark card.
If you put the card as close to the eye as possible think of it as another lens in your eye. And the image was already inverted - it was projected on your retina and your brain automatically re-inverted it so up was up and down was down.
There is no way how pinhole projection can not be inverted. There is no reason to make camera lenses that won't invert the image - the drawbacks of design are far more serious that dumping the chip in correct order, see basics of operation of CCD, (digital cameras), turning the film correctly when developping (film cameras) and adding pentamirror ([D]SLRs' viewfinder). Note that waist-level cameras have inverted viewfinder.
OK, there is one, but it is a Heath-Robinsonian solution: Build your camera with pinhole, translucent screen, another pinhole and the film/CMOS/CCD. This way you'll have inverted image on the screen and double-inverted image on the film.
If you want to see the pinhole effect, find a room, cover all windows except for one small hole. The room will be completely dark, except for the projection of the outside world on the wall opposite to the hole. You will be inside the camera obscura.
