wileyonlinelibrary.com/journal/phpp Photodermatol Photoimmunol Photomed. 2018;34:130–136.
© 2017 John Wiley & Sons A/S.
Published by John Wiley & Sons Ltd
Accepted: 18 October 2017
Quantifying the visual appearance of sunscreens applied to the
skin using indirect computer image colorimetry
| Pegah Kharazmi
| Tim K. Lee
| Sunil Kalia
| Harvey Lui
Department of Dermatology and Skin
Science, University of British Columbia &
Photomedicine Institute, Vancouver Coastal
Health Research Institute, Vancouver, BC,
Departments of Cancer Control Research
Program and Integrative Oncology - Imaging
Unit, British Columbia Cancer Agency,
Vancouver, BC, Canada
Department of Electrical and Computer
Engineering, Biomedical Engineering
Program, University of British Columbia,
Vancouver, BC, Canada
Vincent Richer, MD, FRCPC, Department of
Dermatology and Skin Science, University of
British Columbia & Photomedicine Institute,
Vancouver Coastal Health Research Institute,
Vancouver, BC, Canada.
VGH and UBC Hospital Foundation; Canadian
Dermatology Foundation; National Sciences
and Engineering Research Council (grant
Background: There is no accepted method to objectively assess the visual appearance
of sunscreens on the skin.
Methods: We present a method for sunscreen application, digital photography, and
computer analysis to quantify the appearance of the skin after sunscreen application.
Four sunscreen lotions were applied randomly at densities of 0.5, 1.0, 1.5, and 2.0 mg/
to areas of the back of 29 subjects. Each application site had a matched contralat-
eral control area. High- resolution standardized photographs including a color card
were taken after sunscreen application. After color balance correction, CIE L*a*b*
color values were extracted from paired sites. Differences in skin appearance attrib-
uted to sunscreen were represented by ΔE, which in turn was calculated from the
linear Euclidean distance within the L*a*b* color space between the paired sites.
Results: Sunscreen visibility as measured by median ΔE varied across different prod-
ucts and application densities and ranged between 1.2 and 12.1. The visibility of sun-
screens varied according to product SPF, composition (organic vs inorganic), presence
of tint, and baseline b* of skin (P < .05 for all).
Conclusion: Standardized sunscreen application followed by digital photography and
indirect computer- based colorimetry represents a potential method to objectively
quantify visibility of sunscreen on the skin.
colorimetry, photoprotection, sunscreen
1 | INTRODUCTION
Sunscreens are a pivotal part of the prevention armamentarium against
Food and Drug Administration mandates that commercial sunscreen
products be labeled with their sun protection factor (SPF)
turn is calculated as the ratio of skin’s reactivity to artificial ultravio-
let (UV) radiation with and without the application of a standardized
sunscreen. Ultraviolet reactivity can be determined as a physiologic
threshold response referred to as the minimal erythema dose (MED)
and defined as the lowest dose of UV radiation required to generate
erythema with clear borders that is perceptible 24- hour after expo-
sure. In the United States and Europe, SPF is specifically determined
by dividing the skin’s MED with 2 mg/cm
of applied sunscreen by
the MED of untreated skin.
In real- life conditions, sunscreens are
applied at levels that are significantly lower than those used for SPF
even by patients at risk for skin cancer or those with photo-
The literature suggests that typical real- life application
is more likely to be around 0.5- 1.0 mg/cm
Furthermore, there is a
relationship between amount of sunscreen applied and the measured
Consequently, patients are likely to get lower sun protection
than what is stated on the sunscreen product label.
riers to optimal sunscreen application include concerns over sunscreen
Preliminary data were previously presented at the 24th Annual Photomedicine Society meet-
ing (San Francisco, 2015) and at the 23rd World Congress of Dermatology (Vancouver, 2015).