Effects of image quality, size and camera type on forest light environment estimates using digital hemispherical photography
Effects of image quality, size and camera type on forest light environment estimates using digital hemispherical photography
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DOI：
10.1016/j.agrformet.2004.06.002
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发表时间：
2004-11-20
影响因子：
6.2
通讯作者：
Kawahara, Y
中科院分区：
文献类型：
--
作者：
Inoue, A;Yamamoto, K;Kawahara, Y
数字半球面摄影是估算森林冠层下光环境的有效手段。在这项研究中，研究了不同的图像质量，尺寸和相机类型对使用数字半球面摄影的光环境估计的影响。我们使用Coolpix 900和990两台数码相机，以及独家的鱼眼转换器FC-E8，在15个不同光环境下拍摄了所有可选择的图像质量和大小组合的半球形照片，然后估计了间隙率和冠层开度。使用两个相机所做的估计与图像质量没有差异。相比之下，用Coolpix 900估算的图像大小不同，但与用Coolpix 990估算的图像大小相同。这些结果表明，基本质量和全尺寸图像对于Coolpix 900来说是足够的，而基本质量和vga尺寸是Coolpix 990的最佳组合。对比两相机的最佳组合图像，Coolpix 900产生的间隙率和冠层开度显著高于Coolpix 990。因此，有必要明确说明在进一步的研究中使用的相机类型，以便可以比较从不同的相机获得的结果。总之，尽管数字半球形摄影将是估计光环境的一种方便手段，但我们应该注意本研究中图像大小和相机类型的影响。(C) 2004 Elsevier B.V.版权所有
Digital hemispherical photography is an effective device for estimating the light environment beneath a forest canopy. In this study, the effects of different image quality, size and camera type on the light environment estimates using digital hemispherical photography were examined. Using two digital cameras, Coolpix 900 and 990, with the exclusive fish-eye converter FC-E8, we took hemispherical photographs of all selectable combinations of image quality and size in 15 stands with various light environments, and then estimated the gap fraction and canopy openness. The estimates made using the two cameras did not differ with the image quality. By contrast, the estimates made with Coolpix 900 differed in image size, but not those made with Coolpix 990. These results suggested that the basic-quality and full-size image was adequate for Coolpix 900, whereas the basic-quality and VGA-size was the optimum combination for Coolpix 990. Comparison of the best combination images between two cameras showed that the Coolpix 900 produced significantly higher gap fraction and canopy openness than Coolpix 990. It is therefore necessary to state clearly the type of camera used in further studies, so that the results obtained from a different camera could be compared. In conclusion, although digital hemispherical photography would be a convenient means for estimating light environments, we should pay attention to the effects of image size and camera type presented in this study. (C) 2004 Elsevier B.V. All rights reserved.