Luis Bravo Pereira

For many years filters like the Kodak Wratten E series, or the equivalent Schneider B+W 415, were used as standard UV cut filters, necessary to obtain good quality on UV  Fluorescence photography. The only problem with the use of these filters is that, when they receive the UV radiation that they should remove, they present themselves an internal fluorescence as side effect, that usually reduce contrast and quality on the final image.
With this article we present the result of our experiences on using some innovative filters, that appeared available on the market in recent years, projected to adsorb UV radiation even more efficiently than with the mentioned above pigment based standard filters: the interference filters for UV rejection (and, usually, for IR  rejection too) manufactured using interference layers, that present better results than the pigment based filters. The only problem with interference filters type is that they are sensitive to the rays direction and, because of that, they are not adequate to wide-angle lenses.
We have tested and compared for this article the internal fluorescence for three filters: the B+W 415 UV cut (equivalent to the Kodak Wratten 2E, pigment based), the B+W 486 UV IR cut (an interference type filter, used frequently on digital cameras to remove IR or UV) and the Baader UVIR rejection filter (we used two versions of this interference filter).
The final quality of the UV fluorescence images seems to be of a superior quality when compared to the images obtained with classic filters.

With this paper we are presenting a new promising approach to digitalization of radiographic image in film, using common photographic cameras as device to digitalize with different levels of exposure (allowing, in some cases, to read information from the darker/denser areas of the image) and combining those images with the new technique of High Dynamic Range (HDR) imaging, increasing this way the exposure latitude of the final image. This new approach is possible today because the most recent generations of image treatment software present this new feature. Examples of software presenting this tool are the market leader Adobe Photoshop (presenting this HDR capacity since CS2 version) or the most HDR specialized Photomatix, among others. The resulting images seem to show in some cases more interesting results than the single pass digitalization of images, with or without post-processing improvement, and can in some cases be a good alternative to the use of negatoscopes on the exam of radiographies.

The application of digital photography in the non-invasive examination and documentation of paintings and sculptures has had a growing interest in the Art World. With recent developments of digital photography some cameras present today the ability to record images at different wavelengths of electromagnetic radiation, making it possible today to capture images in different bands of the electromagnetic spectrum, either in the visible spectrum or in the spectrum of infrared and ultraviolet radiation. This allows to obtain images that some scientists describe as “multispectral images” (or, according to other authors, “multichannel images “), which allows the study of works of art in a non-invasive way, allowing the identification of degraded zones, retouches, underlying drawing, etc., complementing traditional exams already used in the study of works of art, as for example UV-fluorescence, IR reflectography and radiography. The present communication will show examples of experimental multispectral imaging studies conducted in wall paintings (prehistoric) and oil on wood paintings (sixteenth and seventeenth centuries). We also make mention here to the difference between this type of image-based exams and other exams known as multi- and hyperspectral analysis.