My Sciographs are all made with the same basic elements:
1. An open, rectangular steel box frame with a translucent screen (the receiver) . This frame comprises (more or less) the possible focal depth of the shadow fields thrown by the lighting instruments. It gives me a structure with which to arrange objects in the shadow field/s and a framework for the receiver. The frame is 18″ X 36″ and was built while I was still working out the principles of this work – this is the 3rd iteration – it will certainly evolve in the 4th.
2. Lights – mostly tungsten fresnels (with occasional appearances by other light instruments). Fresnels are – for many reasons – the commonly available instrument best suited for the widest range of sciographic effects and the best for the imitation of ‘natural’ light like sunlight. They are also surprisingly complex, especially older, tungsten fresnels. Newer LED fresnels eliminate some of the design issues and are very promising for this work. This will be the subject of another post.
3. Objects that block the light and throw shadows (occluders).
The magic is in how those elements work together. Just as the elements of a camera (lens and aperture) and the chosen focal point determine the depth of field of a photograph, the elements of a sciograph determine the focal depth of a shadow. The simplest way to explain focal depth is that an occluder closest to the receiver (the surface on which the shadow falls) will always throw the sharpest, clearest shadow. The farther the occluder is from the receiver, the softer the shadow will become. Put differently, the farther the occluder is from the receiver, the larger the penumbra and the smaller the umbra until eventually the umbra disappears altogether.
However, a shadow field created by a very small (like an LED) or distant light has much greater focal depth than a shadow field created by a large light source. Because of that, shadows in a field thrown by a small light source will appear sharp even at some (relative) distance from the receiver. This is what I mean by ‘focal depth’. By using different kinds of light sources, configured in different ways, it’s possible to create very complex compositions of shadows, just like what happens with ‘natural’ light all the time:
This is what the rig for the microscope image looked like:
Only three objects were used to throw the shadows:
It was lit with 3 sources – this is where it gets a little complicated:
The source on the left is a 750 watt theatrical tungsten fresnel reflected in a slightly convex circular mirror. The convex mirror has three effects: it diminishes the size of the light source thereby increasing the focal depth of the shadow field. Again, that means that occluders can be farther from the receiver and still appear to be ‘in focus’. Because the convex mirror causes the rays of light to diverge it also enlarges the size of the shadow relative to the occluder while simultaneously decreasing the light’s intensity. By itself, this light throws this shadow – note the sharp line of the right side of the microscope and the relative focus of the stencil:
The light on the bottom right is a standard 1ooo watt cinematic tungsten fresnel. The light has been scrimmed to balance the output of the 750w light reflected in the convex mirror on the left. Relative to the reflected light, it is a ‘large’ source, even though it is basically the same size and kind of instrument. The shadow field created by this source has significantly less focal depth than the field created by light reflected from a convex surface. By itself, this light throws this shadow:
The light in the top middle is an odd fixture that I believe was made as an architectural drafting light. It is a 250 watt light meant to be mounted on a table or desk. It is not a fresnel; it has a hammered parabolic reflector surrounding the lamp and an egg crate in front. The combination creates very soft, multiple shadows. By itself, this source creates this shadow:
The combination of these three light sources and the placement of the objects creates the final image:
The possible complex interactions between the elements go far beyond what I did here. For example, it is possible to actually bend light by taking advantage of what is called the ‘shadow blister effect’, making straight lines curve. It is possible to create wave interference patterns using diffraction grids arranged in various locations in the shadow field that will reverse tonality, flipping ‘positive’ shadows to ‘negative’ (light) shadows. You can find these and other effects in many of my images on this site. I plan to post detailed explanations of them as time permits.