Category Archives: W

White balance

The white balance adjusts the scanner’s camera to the prevailing lighting conditions to ensure a uniform color temperature and thus constant image quality. The color sensitivity of the sensor is thereby adjusted to the respective lighting conditions.

The perception of white is strongly dependent on the environment and the respective light source. In daylight, a pure white appears colder than in fluorescent light, for example, where it appears greener. Even in a controlled environment, this can become a problem.

While the human eye or brain can adjust to the respective light situation and quasi intuitively performs a white balance and compensates for color casts, a digital camera mercilessly reproduces them: If the digital camera is set to daylight, for example, and the picture is taken in artificial light, the image will appear reddish.

A user-defined white balance directly during installation therefore guarantees accurate colors right from the start. Since a change in the lighting environment always necessitates a new white balance, a constant and uniform lighting situation should generally be ensured when using planetary scanners.

White balance should be achieved by means of a full-format scan of a surface that is as white or at least neutral gray as possible. Plain white paper is often used for this purpose, but it often contains optical brighteners and can therefore lead to distorted results with color casts.

At book2net, we therefore use high-precision, spectrally neutral white balance targets to ensure precise user-defined, in-camera white balance under local lighting conditions.

Watermark

A watermark is an identifying image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light (or when viewed by reflected light, atop a dark background), caused by thickness or density variations in the paper. Watermarks have been traceable for handmade paper since the 13th century, originally serving as trademarks of the manufacturing paper mills. Since the screens for paper production only had a limited service life and paper was usually not stored for long due to its high price, it is possible to date historical papers very precisely by determining datable watermarks and comparing them with the deviations caused by the manufacturing process. For this reason, filigranology (watermarking) has established itself as a forensic auxiliary science for historical sciences, especially in art history, to determine the age, origin and authenticity of documents and graphic works of art using watermarks. For this purpose, extensive historical collections have been created since the beginning of the 20th century, many of which are now available as databases. Watermarks on papers that have been damaged, poorly preserved or extensively painted over can also be made visible again with the help of modern analysis methods such as multispectral photography. Nowadays, watermarks are mainly used as security features on bank notes, postage stamps, and other government documents to discourage counterfeiting. In the course of digitization, however, imperceptible markings and information in media files that can only be detected with certain methods are referred to as “digital watermarks”. As with traditional watermarks, the document and watermark information should be inextricably linked. There is a separate process for each type of media (images, audio, video), which is adapted to the respective coding and data format. At book2net, too, we offer special software modules to protect digital copies with individual digital watermarks.

Work genesis

The genesis of a work of art, i.e. the creation process, can be made visible via forensic examination using multispectral photography. Watermarks, signatures and the analysis of techniques, image carriers, color materials and paper structures can provide information about the places and modes of origin as well as the artistic work process. Scientific research often receive important information about the dating and authenticity of a work of art (original or copy), but also about artistic and economic connections of an artist and his workshop.