Camera Obscura On Wheels Hits the Open Road

A camera obscura is a very simple device. Consisting of a dark chamber, with only a pinhole to let light in, it focuses an image on its inside surface. If you want to take a permanent copy, it’s as simple as installing a photosensitive film inside and managing the exposure time. Sounds like a normal camera, right? The difference is the scale —  a camera obscura is large enough that humans can stand inside and view the image. Usually, they are large stationary rooms. [Physics Girl] took the show on the road by building a camera obscura out of a rented box truck.

The optics of the camera obscura project an image upside-down.

The basic concept is a great one – hire a box truck, and cover the rear opening with cardboard. Cut a small hole in the cardboard, and you’ve created a camera obscura on wheels. The video does a great job of explaining the optical principles behind what’s happening, and there’s even experimentation around how to change the exposure level and focus through modification of the aperture.

The only downside to viewing a camera obscura on video is that you can’t appreciate the resolution and detail visible in real life. Trust us though, it’s better than any HDTV on the market today.

The rolling camera obscura makes for a great experiment which requires little more than some cardboard, tape, and a sunny day. It would be great fun to execute as an educational activity at a school or makerspace. Once you’ve tackled that, perhaps consider the digital version. Video after the break.

[Thanks to Baldpower for the tip!]

18 thoughts on “Camera Obscura On Wheels Hits the Open Road

  1. Wow! That’s a fantastic idea! Also, the resolution is higher than any HDTV is because its using light from real objects in much the same way your eyes do, it would have even better resolution if our wetware cameras had a higher “pixel” density. This would be a great set for a music video!

        1. It is more like the size of the “blur circle” on the screen or sensor that is produced by any point source. The optimal hole size for the rental truck – assuming f = 2.5m or about 8 feet from door to screen, and green/yellow light – is 2.3mm if I did it right. This will be really dim but much sharper than the images in the video. The F-ratio in this case is about 1000.

          1. See also “disc of confusion” and calculating things like the hyperfocal length.
            I found it all really clicked with me once I started thinking about individual rays of light and for any given starting point, how many places could it project onto (so, for objects at given plane, if it’s further away or a smaller aperture then both will reduce the disc of confusion)

    1. ““Consisting of a dark chamber” incredible! A camera obscura is a dark chamber. Learn something every day :-) I guess they don’t teach Latin in school anymore. ”

      Hell they barely teach English anymore, why would they teach Latin?

  2. The city of Edinburgh has a large tower housing a camera Obscura that looks over the city. The building also houses a collection of optical illusions and holograms (including a holographic microscope which you can look through which is pretty cool).

  3. You’ll need to secure that heavy roll up door in place before moving the vehicle! The wooden doors usually weigh a few hundred pounds when you combine all of the panels. So bear that in mind when fouling the door to stop it moving. Nothing like having the door roll back down a couple panels and then you hit the brakes. Tends to send the door out the top of the tracks and “Murphy” usually sends it at a slight skew that bends tracks to junk.
    You’ll get to pay for the door & tracks, plus any damage it caused to the cargo box.

  4. There was an episode of the Bloodhound Gang on 3-2-1 Contact where the Bloodhound gang gets kidnapped and put in the back of a box truck and they use a pinhole in the back of the truck to make a camera obscura to figure out where they are being taken.

  5. I live in an attic apartment in a historic district. There is a beautiful church just across the way. In the morning the sun rises behind its steeple. Its really quite beautiful. This summer my air conditioner was struggling to keep up with the heat so I foiled over my windows and view. One morning laying in bed trying to awaken in the darkness….I looked over and noticed a small hole in the foil of one window had light beaming through….as my eyes followed it I received a great surprise….

    There on my floor…
    ALL around the bright sunbeam penetrating my darkened room….
    The entire cathedral roof laid out in such detail that I could see each the detail of each rooftile.
    I realized immediately “camera obscura”….sadly I am no davinci and my tracing of the image did it no justice
    Imagining the first time someone else had allowed a single beam of light to sneak passed only to find an entire worlds image carried with it…….
    Hundreds of years late……I still enjoyed my petit eureka!

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