Effect of settings of digital fisheye photography to estimate relative illuminance within forest under low light conditions |
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| Authors: | Kazukiyo Yamamoto Kenji Kobayashi Toshiro Nonoda Akio Inoue Nobuya Mizoue |
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| Institution: | (1) Laboratory of Forest Environment and Resources, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan;(2) Japan Science and Technology Agency/CREST, Tokyo, Japan;(3) Faculty of Agriculture, Nagoya University, Nagoya, Japan;(4) Mie Prefectural Forestry Research Institute, Tsu, Japan;(5) Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto, Japan;(6) Faculty of Agriculture, Kyushu University, Kyushu, Japan |
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| Abstract: | In order to evaluate the effects of settings of digital fisheye photography on estimates of relative illuminance (RI) within
a forest under low light conditions, we assessed the effectiveness of some estimators, i.e., canopy openness (CO), sky factor
(SF), and diffuse transmittance (DIF). The estimates were calculated from digital hemispherical photographs taken with two
different exposure settings, i.e., the reference exposure setting and the auto-exposure setting. We also presented a new estimator
(%Exposure), which does not require image analysis, and compared it with other estimators calculated from a digital hemispherical
photograph using image analysis. The CO, SF, and DIF calculated from digital hemispherical photographs taken with auto-exposure
setting were not significantly correlated with RI. However, those calculated from digital hemispherical photographs taken
with reference exposure settings were significantly correlated with RI. On the other hand, %Exposure showed a slightly higher
correlation with RI compared with the other estimators. |
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