Miscellaneous Imaging Methods

Thermographic Imaging

Two kinds of thermocameras were tested, using short (2-5µ m; Inframetrics) and long wavelenghts (8-12µ m; Agema). These kinds of infrared cameras record the temperature variations on surfaces. The papyri background and the writing could have slightly different emissivities, or they could absorb heat in slightly different manners. Unfortunately the glass plate is not translucent in these infrared wavelengths, so that the cameras could only record the temperatures of the glass surface itself (with the fingerprints upon it).

X-ray Imaging

X-ray equipment had a similar problem with the glass plate as did the thermocameras. The plate was taken to Helsinki Central University Hospital, and tested with varied energies, exposure times and intensities. With 12 bits of grayscale depth nothing was found.

Stereographic Imaging

Stereographic imaging was supposed to find the depth variances of the writing with respect to the surface. It is known that when one writes upon a stack of papers, the writing can be deduced from several sheets below from the small grooves caused by the pressure of the pencil. If the papyri material were soft enough, the untouched surface should be a little higher than the areas inside characters.

A stereographic microscope was used to observe the supposed minuscule variations in depth. With large magnification, the fibers of the papyri were clearly visible, and the structure was identifiable to one of a plant. Unfortunately, this method did not reveal any detectable depth differences from the characters.

Although the script isn't lower than the background, the magnification and depth effect of a stereomicroscope helps discriminating other black marks in the background from the script. The black marks are usually caused by special surface structure, such as crevices and small cracks, and are easaily identifiable with a stereomicroscope.

Video Recording

To avoid the limitation of the straight angles needed in photography, live video recordings were made from a session of studying the plate.

By moving and turning, different areas of the writing can be found easier to read. Photography cannot do that. The only way to record this would be taking the whole process to video. There is at least one problem: the viewer cannot follow the thoughts of the recorder, and it is not intrinsically clear where the point of interest is going to be, and thereby the viewer may frustrate quickly. If the recorder controls his/her actions by rehearcing his/hers movements, masters the camera techniques (proper focusing etc.) correctly and moves the plate always slowly, this could be avoided.

The rotation and movement of a plate gives a wholly new angle in perception. The human eye sees more than a series of pictures; we see a flow with no interrupts, and can automatically detect different dynamical visual properties. For example, while rotating a plate, the background may fade from one shade of gray to another in a different way compared to the text. Grabbing scenes from a video session would produce a series of pictures which highlight different parts of texts, but the dynamics of motion would be less visible.

In principle, a sequence of frames contains more information than any corresponding single frame. A completely another story is how to benefit from this information. Further tests are recommended to find suitable patterns of movement and rotation to record. The live video recordings could at least be used as demonstrations of the importance of illumination and nature of the plates.

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Antti Nurminen, 34044T, andy@cs.hut.fi