Toward a Non-Linear Grayscale Calibration Method for Legacy Photographic Collections
Grayscale image analysis provides a useful means of extracting both stratigraphic depth series and quantitative data useful for compositional analysis of sedimentary cores and lithologic sections. For quantitative application of the method, the user should always consider the context of the complete imaging system (acquisition, processing, storage, output) from which the data arose. Our results demonstrate that bias of mid-tone grayscale values is more sensitive than bias of highlights or shadows. When corrections are applied to the grayscale values that take this nonlinearity into account, the resulting grayscale values compare favorably with sediment carbonate content, a strong influence on sediment brightness in the sediments that were studied. Future implementation of grayscale image analysis will benefit from comparative measurement of sample and grayscale standards to account for this source of bias.
KeywordsGrayscale image analysis Non-invasive sampling Deep Sea Drilling Program Ocean Drilling Program JOIDES Resolution ODP Leg 100 ODP Leg 162 Sediment core photography Marine stratigraphy
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