Home About Us Laboratory Services Forensic Science Communications Back Issues January 2009 research Figure 16: Identification of low-resolution...

Figure 16: Identification of low-resolution (1024 by 768) c1 Canon SD200-1 images

Figure 16: Identification of low-resolution (1024 by 768) c1 Canon SD200-1 images

Identification of low-resolution (1024 by 768) c1 Canon SD200-1 images

This figure shows the result of experiment for identification of low-resolution (1024 by 768) c1 Canon SD200-1 images. It depicts the correlation of pattern noise, in low-resolution (1024 by 768) images from camera c1, with 12 reference patterns. The reference pattern c1–1 is estimated by averaging 200 images captured at a resolution of 1024 by 768, whereas the reference pattern c1-2 is estimated by averaging 200 images captured at a resolution of 2048 by 1536. Correlations, rho, are displayed on the y-axis, while the index of the image being correlated is displayed on the x-axis. The correlation values with reference pattern c1-1 are depicted using small blue hexagonal symbols. The pattern is depicted as a smattering of the symbols, which range from approximately 0.10 on the y-axis and 1 on the x-axis to .05 on the y-axis and approximately 350 on the x-axis. The correlations with reference pattern c1-1 are centered on approximately 0.11 for the first 200 images (1 through 200 on the x-axis) because these images were also used to generate the reference pattern, c1-1. The remaining images, 201 through 325, have slightly lower correlations centered on approximately 0.05. The correlation values with reference pattern c1-2 are depicted using small green asterisks. The pattern is depicted as a smattering of the symbols, which range from approximately 0.04 on the y-axis and 1 on the x-axis to .04 on the y-axis and approximately 350 on the x-axis. The correlations with reference pattern c1-2 are centered on approximately 0.03 for all of the images (1 through 350 on the x-axis). Correlation values with both the reference patterns c1-1 and c1-2 are still significantly greater than the correlation values with other camera reference patterns. Thus, even for the cases when sizes of training and testing images are different, the classification accuracy is close to 100 percent, although with a smaller tolerance and, thus, lesser reliability. Camera c1 is a Canon PowerShot SD200.