The students will build the cameras (Fig. 1) by themselves of matt-black cardboard and other simple materials. The work is comparatively easy, but care is needed in building the camera and making the exposure.
You will need:
Two A4 (or one A3) sheets of matt black cardboard;
Clear and black tape;
A piece of matt or semi-matt b&w enlarging paper. Ilford Multigrade IV has suitable sensitivity for this method;
A pinhole (see “Practical Instructions & Drawings”);
Scissors or Hobby knife (optional);
Add a pencil, ruler and some dexterity – and soon your camera is finished.
Note: The bigger photo shops sell enlarging paper. Many internet shops sell it too. Other materials are easy to obtain in situ.
Making the Exposure:
You need a window with free view to east (or west for sunset), preferably with clear horizon line;
Find the sunrise/sunset point in the horizon. At equinox, Sun rises due east and sets due west;
Turn the camera so, that the line along the right edge points in the direction of the sunrise (Fig. 2 and 3). In the southern hemisphere, the left edge must point in the direction of the sunrise;
For sunset, the left edge of the camera must point to the direction of the sunset;
Level the camera with the help of a water level;
Make exposures for some days. At least one cloudless morning/evening is needed.
What does the sunrise look like on a pinhole image?
If all procedure was well done your pinhole image should look as the following.
The sunrise should have a small curvature that depends ate the latitude you live. In fact the change of this curvature with latitude is one of the subjects this projects is all about. When images start to be posted on the website you should choose other schools images to compare with your own.
Why does the image have this aspect?
The Sun seems to draw a sinusoidal curve during the day.
The amplitude of the curve depends on latitude. The nearer the pole you are, the smaller is the amplitude. This image is made around midsummer at 68.5 degrees N, in Finnish Lapland. Exposed 11 days with four curved-back pinhole cameras for a 360 degree view.
Normally, at lower latitudes, only the upper part of the curve is seen.
The visible part of the curve depends on the date, too; in winter the Sun is lower in the sky, and we see less of the curve.