Developing inter-comparability for high dynamic range devices used to measure light pollution in high-contrast environments.
The EU Green Public Procurement Criteria for Road Lighting and Traffic Signals highlights light pollution as a major environmental and safety concern. Light pollution can be bright (e.g., surface glare) or dim (e.g., overspill from traffic lights) and is disruptive to both humans and animals. Due to the high levels of contrast found in natural environments (e.g., bright light beside shadows), measuring light pollution can be challenging. A single capture from a camera only produces a meaningful image over a limited ‘dynamic range’ of luminosities, outside of which detail is lost. High dynamic range (HDR) capture preserves detail by combining several exposures of the same image. Although this method is useful, commercial HDR systems lack uncertainty statements and traceability, making comparisons between systems impossible and limiting their use.
This project will develop algorithms for generating HDR images and comparing images from different devices. It will model HDR luminance measurements, using this to define requirements for traceability and inter-comparability, and create high-contrast reference materials to characterise the dynamic ranges of commercial instruments. It will develop guidelines for HDR uncertainty budgets and produce a report on the relevance of existing HDR testing methods, contributing as well to standards developed by the International Commission on Illumination.Traceability will allow multiple HDR systems to be used for on-site measurements, granting flexibility, and expanding the range of conditions open to research. This will accelerate the uptake of HDR in this field and allow for a fuller understanding of light pollution, its sources, and its effects.