UV reflectance photography of skin: what are you imaging?

Abstract

Objective Photography can be a powerful tool for researching the skin. Moving outside the visible spectrum and into the ultra violet (UV) presents a unique set of challenges to the skin photographer because of the restrictions imposed by the equipment being used. This article discusses these challenges in relation to camera sensitivity, lens and filter transmission and lighting spectrum, with the aim of demystifying what is actually being captured when imaging skin. Methods In addition to a discussion of existing data on the subject of camera sensor sensitivity, filter transmission and flash spectral analysis, transmission in the UV of a variety of camera lenses using a new method has been carried out. Results Using the described approach, lens transmission between 280 and 420 nm of a range of lenses has been measured. Combining this with camera sensor sensitivity data and filter and light source characteristics, it has been possible to determine an overall, harmonized, spectral sensitivity curve for what is being imaged with a given setup. Conclusions UV reflectance photography, while a powerful tool, is often misunderstood and misreported as to what is actually being imaged. By combining measurements on camera sensitivity, lens and filter transmission and light source spectra the researcher can more fully understand what is they are actually measuring, thereby enabling better communication with the consumer on what they are seeing and a more complete description for any claims support.

Ultraviolet Fluorescence Photography—Choosing the Correct Filters for Imaging

“…For instance, if a light-emitting diode (LED) light source is used, then than is likely to be a more tightly confined wavelength range. If a flash-based light source is being used, then that too gives a wide range of emitted light, more like the spectral signature shown here [ 30 ]. The degree of fluorescence of some of the filters was very low, and capturing that on a camera meant that high ISOs were needed, which can introduce digital noise into an image due to the increased sensitivity.…”

Monochrome Camera Conversion: Effect on Sensitivity for Multispectral Imaging (Ultraviolet, Visible, and Infrared)

“…One of the key benefits of these types of conversions is the ability to image beyond the visible part of the spectrum in the UV and IR. The use of UV for reflectance imaging has been reported for a wide range of applications, such as forensics [ 21 , 22 , 23 ], skin imaging [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ], lepidopterology [ 33 ], botany [ 34 ], and historical conservation [ 35 , 36 ]. With a multispectral conversion which retains the CFA filter, the sensitivity in the UV drops rapidly, from 400 nm until around 350 nm, driven by absorption by the dyes in the CFA filter [ 37 ].…”

Towards an Effective Imaging-Based Decision Support System for Skin Cancer

“…Thus, it is passible of being imaged with a standard digital camera. Though, recent, UV fluorescent photography has been indicated as a valuable tool for the evaluation of tumor margins in BCC cases, while UV reflectance has shown good input in the appraisal of skin photoaging (Mojeski et al, 2020;Crowther, 2020;Pratt et al, 2017).…”