Category Archives: V

VIS spectroscopy (also VIS spectrometry) is a variant of spectroscopy in which the reflection or absorption of light in the visible spectral range (VIS for short) in the wavelength range from approx. 400 to 780 nanometers is measured on the surface of an object. It is used for qualitative and quantitative analyses, among others in forensics and art technology.

Particularly in art technological investigations, this is often done in combination as UV-VIS absorption spectroscopy. This allows the identification of pigments (mostly inorganic) and dyes (organic) independent of their carrier material (paintings, graphics, murals, furniture, textiles, etc.).

The method uses the selective interaction of electromagnetic radiation from the visible light and its adjacent wavelength ranges with the materials to be examined; part of the irradiated light is absorbed, part is reflected. This results in a specific spectrum for each material, an optical fingerprint, so to speak. This can be compared with reference materials and thus lead to an identification of the colorant.

In photographic technology, optical vignetting (edge decoration) is an effect that may be wanted in artistic photography, but is not desired when digitizing documents, which require a true-to-original capturing. Vignetting is essentially a decrease in brightness towards the edge area of the image, which is caused by the light guidance through the objective and the axially arranged openings connected to it.

The resulting images are significantly darker due to the drop in light from the edge and mostly the “lighter” center of the image is shown in a circle.

In order to avoid this effect with our scanners, we work with special lenses in which this effect has already been corrected, unlike conventional camera lenses. Subsequent image manipulation or correction using software is therefore not necessary.

Vignetting

When taking a picture with a microscope through the eyepiece. This photo was taken “freehand” with a compact camera above the microscope eyepiece.
Due to lack of optical adjustment, the edge of the camera sensor cannot be exposed.

Source: Wikipedia Commons (unchanged)  Copyright: Creative Commons Attribution-Share Alike 3.0 Unported

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The V lambda curve is a luminous efficiency function or luminosity function describing the average spectral sensitivity of the human eye, which it perceives in daylight. The visible spectral range from 380 to 780 nanometers is perceived as light in the human eye.