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Fig. 6 | Botanical Studies

Fig. 6

From: Sky-canopy border length, exposure and thresholding influence accuracy of hemispherical photography for complex plant canopies

Fig. 6

Cropped binary images of model CHPs with the ETM extents ranging from − 7 to + 9 stop. (a)–(d) are the original images of model CHPs acquired with exposure manipulation of − 2, 0, + 2 and + 4 stop. (e)–(ab) are the binary images obtained with combinations of 4 exposure manipulations (− 2, 0, + 2, and + 4 stop) and 6 thresholding manipulations (− 5, − 3, − 1, + 1, + 3, and + 5 stop). Canopy and grey pixels which are misclassified as sky pixels are shown in red; sky and grey pixels which are misclassified as canopy pixels are blue; sky and grey pixels which are correctly classified as sky are white; canopy and grey pixels which are correctly classified as canopy are black. These CHPs were taken for a model canopy with gap fraction of 0.25 and SCB length per unit area of 0.4 mm mm−1 (i.e. side length of square opening of 2.5 mm). The diameter of the original circular images of these model CHPs is 2098 pixels, and the image dimension of cropped binary images shown in this figure is 177 by 177 pixels. Greyness histograms of these CHPs presented in this figure are shown in Fig. 7. The unit of the exposure manipulation, thresholding manipulation and ETM extent is stop

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