Reconstruction of cumulative daylight illumination fields from high dynamic range imaging: Theory, deployment and in-situ validation

A novel high-dynamic range (HDR) camera-based approach to measure the cumulative daylight dose in historic/conservation spaces has been devised and tested in a real-world setting under normal viewing conditions. The technique derives illuminance from the HDR-acquired luminance at numerous patches of the wall surfaces visible in the HDR image. These patches serve as proxy illuminance meters, thereby allowing the prevailing illumination field across the entire visible wall to be derived using a Kriging algorithm. The technique was validated under both controlled and in-situ conditions over periods of several months and shown to have comparable accuracy to the illuminance logging devices commonly used in historic/conservation settings. The set-up comprising a consumer digital camera and tethered computer proved remarkably resilient and allowed for continuous monitoring periods of six months or more. Application in a real-world setting revealed operational practicalities that would not have been found in a controlled environment.</div

New tools for managing daylight exposure of works of art: case study of Hambletonian, Mount Stewart, Northern Ireland

This paper describes a project to reduce the excessive daylight exposure of an oil painting, Hambletonian, Rubbing Down, displayed at Mount Stewart, Northern Ireland. Climate-­based daylight modelling (CBDM) was used to understand the light exposure of Hambletonian and to assess the impact of control measures on the annual light exposure and viewing condition of the painting in the winter months. The computer model was used in conjunction with measured lux data to establish the base case light exposure and the effect of the control measures. Light control was implemented through the use of darker paint finishes on the walls and ceiling, which reduced the amount of reflected light reaching Hambletonian;; and the addition of a mesh screen to the outside of the glazed dome above the painting. These interventions were cost-­effective and straightforward to implement and manage. CBDM suggests the interventions reduced Hambletonian’s annual daylight exposure from 3.5 mlxhr to 0.63 mlxhr

Illumination and conservation: a case study evaluation of daylight exposure for an artwork displayed in an historic building

This paper describes the application of climate-based daylight modelling to predict the annual daylight exposure received by an 18th century painting oil displayed on the Stone Staircase at Mount Stewart, near Belfast, Northern Ireland. The simulation predicted that the painting was receiving several times the recommended daylight exposure limit of 0.6 Mlux hrs for this type of artefact. The predictions were compared against the limited monitored data that were taken at the site. Notwithstanding the shortcomings of the monitored data, the agreement with simulation was sufficiently encouraging to allow recommendations to be made regarding interventions to help reduce the daylight exposure experienced by the painting

New developments in understanding daylight exposure in heritage interiors

This paper reports on an investigation into daylight exposure in National Trust (England, Wales and Northern Ireland) interiors. Developing a study of a top lit staircase at Mount Stewart, the focus of this research is the daylight performance of side lit rooms. The multistrand methodology involved: conventional use of light data loggers with a novel camera system based on high dynamic range (HDR) imaging; simulation using climate based daylight modelling (CBDM); and detailed recording of room use by staff. Although integrating this data has proved challenging, early results from both the simulation and the HDR system already provide insights into collections management practises for Trust staff

Improved daylight management of historic showrooms: a methodology based on detailed recording and analysis

This paper describes a pioneering in situ study of the daylight characteristics of a historic house interior. A combination of lux measurements inside and outside a historic showroom and recording of sunshine hours have been used together with a log of the room blind operation to understand the daylight characteristics of the room under different weather conditions, blinds settings and season. Average lux, daily lux hour dose, time below 30 lux and daylight factor metrics have been derived to assess daylight conditions over a 10-month period for both conservation of light-sensitive collections and the viewing experience of visitors. Recommendations are made on how to improve daylight management for conservation and visitor experience