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Ultraviolet Reflected Photography (UVR)

Ultraviolet reflected (UVR) photography is used to enhance the readability of faded paints and inks, and to detect modern white pigments such as zinc white and titanium white. As part of technical photography documentation, UVR is widely applied in the examination of many types of artifacts.

UVR and Technical Photography

Technical photography methods used in cultural heritage are based on the interaction between electromagnetic radiation and materials across different spectral regions. By selecting specific wavelength ranges—infrared (IR), visible (VIS), and ultraviolet (UV)—it is possible to reveal distinct information about the layered structure of an artwork. Each technique records a different type of radiation, such as reflected or emitted light, and therefore provides access to specific features: infrared can penetrate upper paint layers to reveal underdrawings, visible light documents surface appearance, while ultraviolet can highlight varnishes, surface treatments, and material differences. This relationship between spectral bands, imaging methods, and the physical layers of an object forms the basis of technical photography in conservation.

Ultraviolet Reflected (UVR) photography specifically records the ultraviolet radiation reflected by the surface of an object. Unlike UV fluorescence, it does not capture emitted visible light, but differences in UV reflectance between materials.

Photographic setup

Ultraviolet Reflected (UVR) photography records the UV radiation reflected by the surface of an object. Unlike UV fluorescence, it does not capture emitted visible light, but differences in UV reflectance between materials.

Equipment

A full-spectrum modified camera.
A standard photographic lens is generally suitable. Lenses with strong UV-blocking coatings should be avoided when possible.
The UV-pass filter from the Robertina Filters set is mounted on the lens. This filter blocks visible and infrared light, allowing only ultraviolet radiation to reach the sensor.
Fabrizio UV lamp. UVR requires ultraviolet light sources, typically centered around 365 nm. Use two Fabrizio UV lamps positioned symmetrically. Place the lamps at approximately 30° angles to the surface. Ensure uniform illumination across the object. Avoid hotspots and direct reflections

Geometry and positioning

Mount the camera on a tripod, perpendicular to the object
Use a 30° / 30° lighting configuration
Adjust distances to achieve even lighting and minimize glare
This setup helps reduce specular reflection and enhances differences in surface reflectance.

Shooting conditions

Use manual focus and manual exposure
Keep ISO as low as possible to reduce noise
Switch on UV lamps and focus

Faded paint

Ultraviolet Reflected (UVR) photography is used in art examination to enhance subtle differences in surface reflectance that are not visible under normal lighting. It is particularly effective for improving the legibility of faded paints and inks, and for detecting the presence of certain pigments—especially modern whites such as zinc white and titanium white—based on their characteristic response to ultraviolet radiation. UVR can also assist in identifying retouching and material inconsistencies on the surface, providing valuable information for conservation and technical analysis.

This figure illustrates the application of Ultraviolet Reflected (UVR) photography for pigment analysis, showing how different materials respond to ultraviolet radiation. The main use of UVR is the study of pigments, both for identification—particularly of modern whites such as titanium white and zinc white—and for the enhancement of faded paint layers. As visible in the image, most historical pigments appear dark in UVR because they strongly absorb ultraviolet radiation , while a limited number of materials show higher reflectance, allowing their discrimination. This contrast forms the basis for pigment mapping and material differentiation. Further details on this methodology are discussed in the paper “Identification of pigments by multispectral imaging: a flowchart method”, available for download here

Mapping retouches

In this image, we show an application of UVR photography to enhance the visibility of retouching on a painting. This old retouch is barely visible in the UV fluorescence (UVF) image, where it appears only as a slightly darker line and can easily be overlooked. In contrast, UVR imaging significantly improves its readability by increasing the contrast between the retouched area and the original paint. The UVR luminosity image is digitally combined with the visible (VIS) image to highlight the retouch while preserving the original color information, allowing for a more accurate interpretation of the intervention. Further details on this methodology are discussed in the paper “Practical notes on ultraviolet technical photography for art examination.”

Painting Technique

UVR can be useful in highlighting painting techniques. In this image, we observe a detail of a painting where the UV fluorescence (UVF) image does not reveal any differences within the white area. In contrast, UVR clearly shows variations in the materials used for the white shading. This provides valuable insight into the artist’s technique and the use of different pigments or mixtures. Further details on this methodology are discussed in the paper “Practical notes on ultraviolet technical photography for art examination.”

365 nm: The Optimal UV Wavelength

Tests performed on a pigment checker show that using wavelengths shorter than 365 nm does not provide any significant advantage in UVR imaging. In particular, no meaningful differences in pigment behavior were observed that would justify the use of more energetic and potentially hazardous radiation, such as at 330 nm. The reflectance response of the pigments remains essentially comparable, while the risks associated with shorter wavelengths increase. The only notable exception was lithopone, which shows stronger absorption at 330 nm. However, this limited advantage does not justify the use of more energetic and potentially hazardous radiation, as the behavior of the other pigments remains essentially unchanged.

For this reason, Fabrizio UV Lamp at 365 nm represents the most effective and practical choice for UVR photography. Further details on this methodology are discussed in the paper “Practical notes on ultraviolet technical photography for art examination.”

Resources

Publications on Ultraviolet Reflected photography (UVR)
A. Cosentino “Practical notes on ultraviolet technical photography for art examination” Conservar Património 21, 53-62, 2015.
A. Cosentino “Identification of pigments by multispectral imaging a flowchart method” Heritage Science, 2:8, 2014.
A. Cosentino, S. Stout “Photoshop and Multispectral Imaging for Art Documentation” e-Preservation Science, 11, 91–98, 2014.
A. Cosentino “Effects of Different Binders on Technical Photography and Infrared Reflectography of 54 Historical Pigments” International Journal of Conservation Science, 6 (3), 287-298, 2015.

Learn Technical Photography for Art Examination

Technical Photography is one of the most powerful—and often overlooked—tools for the scientific examination of art and archaeology. If you are a conservator, scientist, or art collector and you are not yet familiar with this method, it is truly a missed opportunity. Using simple, affordable equipment and a clear methodology, Technical Photography allows you to reveal underdrawings, retouchings, material differences, and conservation issues in a completely non-invasive way. Far from being complex or inaccessible, it is an easy entry point into scientific analysis. In many cases, Technical Photography represents the first essential step toward a deeper understanding of artworks and archaeological objects.