This is a technique called solargraphy. It is one of the most basic forms of photography. This was taken using a homemade pinhole camera, made from a soap tin. The camera was loaded with black and white light sensitive paper and secured to a fence post for six weeks. The lines in the sky are created by the sun as it moves through the sky, burning the lines you see into the paper’s emulsion. Each line represents one full day, but on cloudy days no lines are made as the sun is not visible. As the days get longer the sun gets higher in the sky, which is why the lines are not all grouped together. In places the lines are dashed, which is caused by the sun passing momentarily behind a cloud.
This exposure was six weeks, however much longer exposures are possible. This photo was produced as part of a project I undertook for Year 12 Photography, however the project has moved beyond that now and has become a collaboration between myself and another photographer named Marc Bongers. We are in the process of setting up a website to display these photos, of which there are many more. Watch this space.