Sitting in a Pinhole Camera

Pinhole cameras are the simplest camera possible, made up of only a pinhole and a screen or film. They don't even need a lens. The camera works by line of sight and the fact that light essentially always travels in straight lines. For every point on the film there is a single line of sight, out through the pinhole, to a point in the world outside the camera. Only light from that point in the outside world can get through the pinhole and hit the film, which is the way in which the image is made. This simplicity means that you can make a pinhole camera incredibly easily. All that is needed is:

1. A dark container or enclosure. 
2. A small circular hole in one side of the container. 
3. A screen or film to detect the light. 

The first two of these are easy to make at home, but the third isn't. Who has a spare piece of film and developing solutions? The [other] solution? Use a person to detect the light and see the image directly, or sketch it on the screen. The problem with people is they are pretty big, you can't squeeze one into a shoebox. Let's make a bigger pinhole camera then, one the size of a room. A room-sized container is easy to find, it's called a room!

A room sized pinhole camera!

The ability of a pinhole to project an image of a scene has been known for over 1000 years, and was first clearly described by the Persian philosopher Alhazen. These ancient scientists faced the same problem detecting light and initially used darkened rooms or tents with a pinhole in one side, then traced the image projected by the pinhole by hand. These devices are called camera obscura, the Latin literally meaning darkened room!

Turning a room into a pinhole camera takes just three easy steps:

1. The dark enclosure 

A pinhole camera container has to be light proof to prevent light leaking in and spoiling the image. The best thing for light proofing a room is aluminium foil which is very opaque for its weight and thickness. Foil tape is also excellent for blocking smaller gaps. 

2. The pinhole
There are a few rules for pinhole size; the bigger it is, the brighter the image. There is simply a larger gap for the light to get in. Unfortunately larger pinholes give a more blurred image because it increases the range of angles at which light can pass through the pinhole and hit a particular point on the film or screen. The pinhole also can't be too small else diffraction of light will start blurring the image. Practically for a room a "pinhole" around 1.5-2.0 cm in diameter will let in enough light to see the image clearly, but be small enough to give quite a sharp image.

3. The screen or film
In a room-sized pinhole camera you just need to sit in the room to see the image!

Foil blocked windows and a pinhole, the shaft of light is from the sun.

The image in a pinhole camera is inverted (upside down). This is because for light to reach the top of the film after travelling through the pinhole it has to be travelling at an upward angle; the line of sight through the pinhole means this is a view of the ground. Similarly for the light to reach the bottom of the film after travelling through the pinhole it has to be travelling at a downward angle, in this case giving a view of the sky. The upshot of this is that in a room sized pinhole camera the floor is a sea of clouds with an inverted picture of the world outside projected on the wall.

The pinhole image the right way up...

... and upside down. The same way up as the image.

You can literally sit in the clouds!

Software used:
UFRaw: Raw to jpg conversion of the raw camera files.

Book Scanning

I have an old book which I am mining data from... The problem is paper is a pain; there is no Ctrl+F function and unless the index includes the terms you are after (which, in this case, it doesn't) then searching turns into a real pain.

The solution? Scan it.
The problem? How to scan it.

Unlike printed, typed or even many handwritten documents it's not easy to pull apart a book and scan the pages with an automatic machine, especially when the book is old, out of print and quite valuable. Most book scanners (including Google's) use cameras instead. This is my setup:

A very high-tech setup.

It's all very simple; a camera, a tripod to hold the camera still, remote shutter button to snap the pictures, lots of lamps for even illumination and a data connection to the computer so I didn't fill up the memory card too fast.

It was a pretty chunky book (801 pages) and it took a total of 489 shots (including reshoots of slightly out-of-focus pages) to capture all of it. That took nearly 1.5 hours, or about 10 seconds per photo. So what does a whole book look like?

With some magic semi-automated processing these images are all that is needed for a perfect scan. Using ImageJ I converted them to black and white, subtracted the background and cropped/rotated the pages. These are some samples:

These processed images can simply be fed into Adobe Acrobat or other similar optical character recognition (OCR) software to translate the image of the text into machine-understandable, fully-searchable text. Exactly what I need!

Software used:

ImageJ: Automated image processing

Adobe Acrobat: OCR

Some more instructables fun... A variable neutral density filter in the cheapest possible way. This can be used to get shallow depth of field (wide aperture) or motion blur even under bright light conditions.


Simple Variable Neutral Density Filter - More DIY How To Projects