In our last blog post, 10 fun facts about Magnifiers, we mentioned one feature of magnifiers (or any lens, really) but kind of glossed over it.
“5) Your magnifier can act as a little projector of sorts – if you have a bright window you can make an image of what is outside that window by holding the lens a little bit away from a wall on a darker area of the room.”
We kind of glossed over this, and didn’t even post a picture of it. But this is a staple of optics and in fact any positive lens can create a real image on a screen. Its pretty much what every movie projector does, although those are much more complex optical systems.
Anyway, here is an image of such a projection. We went to the back of the store and made an image of the windows in the front of the store. Its a bit crude, as it was lit in the store and the original image is upside-down. But you can make out the inverted ‘Sp’ on our window, as well as several of the ceiling lights.
You can pretty much do this with any light source. If you have an unfrosted bulb you can project a large image of the bulb’s filament on any surface using a magnifier.
However, this trick can be used for more than just lights. There is an old optic trick to taking images from the world and projecting them onto a screen in a dark room or some other screen covered by a shade. This is called the Camera Obscura.
Camera Obscuras were optical devices that would use either a positive lens or a pinhole (pinholes can act as lenses) to project whatever is in front of the lens onto a blank screen to be viewed or onto a piece of frosted glass. The latter was used as a primitive camera by early artists: They would use the projection to make drawings simply by tracing the image projected with their camera obscura.
The former method was actually used as a very popular carnival/park/beach attraction back in the day.
The idea of that was fairly simple: you would have a small, dark room or tent. On the top you would have a small turret with lenses. The light from the outside world would enter the lens and be reflected by a mirror that would cause the image to project onto a table’s surface in the room/tent below. The table usually had a curved surface to match any edge errors caused by the lens and get a smooth, focused image.
The viewer would be treated to an almost eerie live image of the world around them. In an age where movies were barely in their infancy and TV non-existent such a live image was quite impressive indeed.
Many public parks had a camera obscura attraction, as did many popular beaches & boardwalks, and come carnivals. Many of them existed in the USA from the late 19th century into the early 20th century. Today, however, only a handful remain in the USA, the most popular being the Cliff House camera obscura just north of San Francisco.
Admission for Camera Obscura was usually low-cost, something like a dime in the 1920’s. The rooms could only admit a few people at a time but upkeep wasn’t too much cost.
However, as movies became more popular, there seemed less reason for the Camera Obscura tourist locations to exist. The idea of a simple projection of an image seemed less impressive. The Great Depression did not help matters as people had little money to spend on entertainment. Many Camera Obscura buildings closed or fell into disrepair. With World War 2 most resources were used for fighting the war. By the time it ended most Camera Obscura were closed, in serious disrepair, or long gone.
The 50’s were not a kind age to things that were popular in the early part of the century. Restoration of small wood buildings in parks & beaches seemed an odd idea to most. Some even pondered why we should go inside to see something we can just stay outside and see. But these folks failed to grasp the beauty and simplicity of the Camera Obscura. Nevertheless any chance at restoring or replacing the Camera Obscura Tents & Booths was gone as recreational attention had gone elsewhere. A tiny handful may have been built in the post-war era and their life was at most a couple of decades.
Today, with the advent of a ‘make-it-yourself’ society that loves to build odd gadgets and items the Camera Obscura is making a small comeback. Using portable tents (or just people’s own rooms) and minimal equipment plenty of folks have built a decent number of Camera Obscura. It’s beauty is in its simplicity: in an age where High-Definition TVs are in every home there is still something magical about an image from a single lens or just a pinhole projecting the outside world live onto a table or screen in a dark room. The fact that it is so simple means almost anyone can do it. Here is a short video of some folks making a pinhole-style with just $70 in materials – most of the cost is black sheeting:
This is just one example, you can find dozens more videos using different materials, etc. Most typical is the pinhole method since it does not involve lenses.
Want to learn more? Here is a link to probably the best Camera Obscura website around. Images of old Camera Obscura sites, pictures, and other great stories.