# Image Quality Assessment of Digital Image Capturing Devices for Melanoma Detection
## 4 Discussion
The TBP implementation in our test applies a built-in DSLR camera with a resolution of \(6000\times 4000\) pixels [37]. The camera is horizontally oriented, and four images must be captured to cover each patient position [6]. However, the number of photos and time for TBP can be reduced significantly by rotating the camera through 90 degrees to capture images vertically instead of horizontally. Upgrading an existing camera with a higher resolution camera (i.e., \(9504\times 6336\) pixels) can replace four horizontally taken images with a single shot image of vertical orientation. That reduces the total number of shots, maintains high image resolution and shortens the time it takes to capture images of a full body significantly. Our results show that images captured with uncalibrated mobile devices or digital cameras may cause notable colour variations. Cameras have difficulty adjusting the appropriate parameters (inappropriate colours and brightness) when operating in automatic mode, especially when using light from a handheld dermoscope. Therefore, the cameras should always be calibrated to minimise colour differences between different imaging devices and the illuminant characteristic. However, almost all digital cameras also allow users to adjust the parameters manually. One of the simplest but effective methods is to adjust the colour white balance (CWB) manually based on the given light conditions. The correct camera exposure time is determined using the reference middle grey background to ensure the correct illumination of the images. This two-step camera calibration procedure improves the colour accuracy of both clinical and dermoscopy images significantly. The results show that colours are much closer to the range of a human eye's detection capability, with a colour error that is smaller, as recommended in Hardeberg [48]. However, the colour accuracy of dermoscopy images can be improved further by using custom colour profiles (ICC). These can be created for a known exposure profile, but can only be generated for RAW images. However, to create an ICC profile, we need software that recognises the differences between standardised colour values and those captured. Such software is already available to professional photographers as a standalone commercial version, or as a third-party software plugin. Using ICC profiles would also be one option for colour correction of dermoscopy images. This method first requires a calibrated target to be able to create an appropriate ICC profile. However, to date, the smallest available target ColorChecker Classic Nano, with its size 24 mm \(\times\) 40 mm, does not match the field of view of existing handheld dermoscopes. Some improvements could be addressed for future work. A specific target should be developed for hand dermoscopes that could improve the colour calibration process as well as a test tool. It can be used both as a calibration tool, as well for testing new devices (i.e., a handheld dermoscopy device coupled with a camera). The target will be based on an attachable glass with a printed test target. The target will allow measuring colour response, resolution and sharpness, and can be combined with colour correction software as a simple camera calibration tool.