TY - JOUR
T1 - A joint validation study on camera-aided illuminance measurement
AU - Mahlab, F.
AU - Yamaguchi, H.
AU - Shimozima, Y.
AU - Yoshizawa, N.
AU - Cai, H.
N1 - Funding Information:
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Hongyi Cai was supported by the University of Kansas for Sabbatical leave to visit the Tokyo University of Science in Japan and participated in the field measurements in Japan.
Publisher Copyright:
© The Chartered Institution of Building Services Engineers 2023.
PY - 2023/10
Y1 - 2023/10
N2 - This joint study conducted in the United States and Japan reviewed existing illuminance measurement methods that use a conventional digital single-lens reflex camera, including (a) per-pixel illuminance calculation using non-fisheye wide-angle lenses, (b) hemispherical projection-based illuminance calculation, (c) the KU method developed by the University of Kansas (KU) and (d) the L-CEPT method developed by the Japanese team for per-pixel illuminance calculation using 180° fisheye lens. Next, laboratory and field measurements were conducted in 32 test scenarios in Kansas and Japan to improve and validate the two similar methods (c) and (d) for per-pixel illuminance calculation and compare them to the simplified method (b) using orthographic projection-based illuminance calculation. Based on the test results, the camera-aided illuminance measurement method could have an error rate of 13.7% ± 15.3% (SD) in all 32 scenarios. Large errors (>25%) were observed in six extremely dynamic gymnasiums with rapidly changing morning sunlight. Alternatively, an average error rate of 7.7% ± 7.5% was observed in the 26 test scenarios without rapidly changing direct sunlight. The simplified orthographic projection-based method could achieve the same level of accuracy as the per-pixel KU/L-CEPT method. Yet, multiple issues on camera-aided illuminance measurement still need further investigation.
AB - This joint study conducted in the United States and Japan reviewed existing illuminance measurement methods that use a conventional digital single-lens reflex camera, including (a) per-pixel illuminance calculation using non-fisheye wide-angle lenses, (b) hemispherical projection-based illuminance calculation, (c) the KU method developed by the University of Kansas (KU) and (d) the L-CEPT method developed by the Japanese team for per-pixel illuminance calculation using 180° fisheye lens. Next, laboratory and field measurements were conducted in 32 test scenarios in Kansas and Japan to improve and validate the two similar methods (c) and (d) for per-pixel illuminance calculation and compare them to the simplified method (b) using orthographic projection-based illuminance calculation. Based on the test results, the camera-aided illuminance measurement method could have an error rate of 13.7% ± 15.3% (SD) in all 32 scenarios. Large errors (>25%) were observed in six extremely dynamic gymnasiums with rapidly changing morning sunlight. Alternatively, an average error rate of 7.7% ± 7.5% was observed in the 26 test scenarios without rapidly changing direct sunlight. The simplified orthographic projection-based method could achieve the same level of accuracy as the per-pixel KU/L-CEPT method. Yet, multiple issues on camera-aided illuminance measurement still need further investigation.
UR - http://www.scopus.com/inward/record.url?scp=85148506052&partnerID=8YFLogxK
U2 - 10.1177/14771535231154169
DO - 10.1177/14771535231154169
M3 - Article
AN - SCOPUS:85148506052
SN - 1477-1535
VL - 55
SP - 571
EP - 593
JO - Lighting Research and Technology
JF - Lighting Research and Technology
IS - 6
ER -