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In 2009, Christopher Cuttle began to challenge the suitability of the metrics contained within current lighting design standards and guidance. In short, Cuttle proposed a move away from providing an amount of light that relates to the difficulty of a visual task and instead, providing an amount of light that relates to the brightness of a space. This sense of brightness would be estimated by a new lighting metric, Mean Room Surface Exitance. The research presented in this thesis strove to examine, critically evaluate, analyse and investigate the merit of changing indoor lighting standards to include Mean Room Surface Exitance. More specifically, the research examined the following: To address issues surrounding derivation and calculation of Mean Room Surface Exitance, Cuttle’s proposed formula to calculate Mean Room Surface Exitance was critically examined and found to be erroneous under certain conditions, with an alternative formula being developed, proposed and validated as part of this research. To address the issue with computation, a script was developed and validated as part of this research and this script allows calculation and computation of Mean Room Surface Exitance through currently available freeware.
To facilitate measurement of Mean Room Surface Exitance in the field, a script was written and validated and this script can be applied, in conjunction with High Dynamic Range imaging technology, to easily, quickly and accurately record measurements once an installation is complete. To examine the relationship between Mean Room Surface Exitance and brightness, three experiments were set up that exposed a group of participants to a range of levels of Mean Room Surface Exitance, with each level delivered across a number of variables that would be experienced in practice. Generally, a linear relationship was found to exist between the level of Mean Room Surface Exitance and the subjective response to brightness. To investigate the relationship between Mean Room Surface Exitance and perceived lighting quality, two experiments were conducted. These demonstrated a strong correlation between the reported perceived brightness and the reported satisfaction with lighting quality. However, this relationship changed when participants were exposed to light scenes that contained extreme non-uniform light distributions; suggesting that whilst the space was bright enough, there is more to good lighting quality than brightness.
Each of the above is a distinct contribution to existing knowledge, but also the first step in a number of different directions, with each moving towards the possible widespread application of MRSE in lighting practice at some stage in the near future.
Duff, J. (2015) On a new method for interior lighting design. Doctoral Thesis, Technological University Dublin. doi:10.21427/D7RS33