# Image Quality Assessment of Digital Image Capturing Devices for Melanoma Detection
## 2 Materials and Methods  
In the study two randomly selected patients were included who underwent a routine dermoscopy examination of the skin moles due to a phenotype with a very high number (>100) of melanocytic nevi, which increased the risk of melanoma appearance. Both subjects gave their informed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of the University Medical Centre, Maribor (Project identification code UKC-MB-KME-17/20). Measurements for melanoma detection imaging were captured using a set of smartphone cameras, including iPhone 5s, iPhone 7, iPhone XR (Apple Inc., Cupertino, CA, USA), Samsung S10, (Samsung Electronics Co., Ltd., Seoul, South Korea) and Huawei P10, (Huawei Technologies Co., Ltd., Shenzhen, China); a high-resolution compact digital mirrorless camera, Canon EOS M10; a DSLR Canon EOS 800D camera, (Canon Inc., Tokyo, Japan); and, a Medicam 1000s camera (FotoFinder Systems GmbH, Bad Birnbach, Germany). The DSLR Canon EOS 800D camera and the Medicam 1000s are combined in the FotoFinder system [37], whereas the DSLR Canon EOS 800D camera is used for capturing images in the high-resolution TBP [38]. The list of cameras, sensor resolutions and parameters of applied lenses are given in Table 1.  
Figure 1 shows the standardised Imatest ISO 12233:2017 edge spatial frequency response (eSFR) target chart used for the standard image quality parameter measurements [39]. It is fully compliant with the Low Contrast Edge Spatial Frequency Response ISO Standard, and integrates elements of several image quality parameter measurements, including sharpness, lateral chromatic aberrations, white balance, tonal response, colour accuracy, and noise [40]. We created the test target in vector  
format, based on the template of the ISO 12233:2017 eSFR target used for standard image parameter measurements. The vector graphic template for printing was prepared in Adobe Illustrator software (Adobe Inc., San Jose, CA, USA). Sixteen colour patches of known colorimetric values and elements for targeting image orientation were placed in an appropriate position on the chart. A customised target enables measuring a number of parameters (i.e., sharpness and resolution, colour reproduction quality, noise, exposure accuracy, dynamic range and ISO Sensitivity) from a single image. It can be printed in any size that meets the sharpness measurement requirements of digital cameras with built-in high-resolution sensors. The chart dimension of \(90\times 135\) cm allows for analysis of the image sharpness for camera sensors with up to 25 Megapixels of resolution. The 16 patch colours on the printed eSFR ISO test chart were determined as CIE L*a*b* values, defined by the International Commission on Illumination (CIE) on a Datacolor 800 spectrophotometer to calculate accurate patch colour values [41; 42]. A diffuse white reflection standard of 8\({}^{\circ}\) measurement field angle geometry was used when the patch was illuminated by a D65 light. The converted colour values of each patch were used as the reference value for colour accuracy analysis. All cameras were operated without a flashlight, except for the Canon EOS 800D camera, where a flashlight was used as a third light source illumination option. The colour measurements on the flashlight were performed additionally because this camera is used for the TBP in the FotoFinder system, where a flashlight is applied by default [37]. Camera settings, such as white balance, shutter speed, aperture and ISO, were next all set on auto mode. The focus point, however, was set manually at the image centre. Figure 2 shows the applied test chart booth settings. The distance from the camera to the chart was adjusted regarding the camera lens view angle, to cover the sensor surface by approximately 90 percent.