Home About Us Laboratory Services Forensic Science Communications Back Issues January 2009 research Figure 13: Mean and standard deviation of p as a...

Figure 13: Mean and standard deviation of p as a function of the JPEG quality factor for c2 compared with all cameras

Figure 13: Mean and standard deviation of ρ as a function of the JPEG quality factor for c2 compared with all cameras

Mean and standard deviation of ρ as a function of the JPEG quality factor for c2 compared with all cameras

This figure displays the mean and standard deviation of rho as a function of the JPEG quality factor for c2 compared with all other cameras. Correlations, rho, are displayed on the y-axis, while the JPEG quality factors, q, are recorded on the x-axis. Eight blue circles represent the mean of rho for camera c2, and passing through each blue circle is a vertical blue line starting from the mean minus standard deviation of rho, up to the mean plus standard deviation of rho. From left to right, for images stored at the best quality factor offered by the camera (known as native) and images resaved at a JPEG quality factor of 100, rho has a mean of approximately 0.065 and a standard deviation of approximately 0.04. For images resaved at a JPEG quality factor of 95, rho has a mean of approximately 0.055 and a standard deviation of approximately 0.03. For images resaved at a JPEG quality factor of 90, rho has a mean of approximately 0.05 and a standard deviation of approximately 0.03. For images resaved at a JPEG quality factor of 85, rho has a mean of approximately 0.04 and a standard deviation of approximately 0.025. For images resaved at a JPEG quality factor of 80, rho has a mean of approximately 0.035 and a standard deviation of approximately 0.02. For images resaved at a JPEG quality factor of 75 and 70, rho has a mean of approximately 0.03 and a standard deviation of approximately 0.02. The mean and standard deviation of the correlations for the other cameras are approximately zero at every JPEG quality factor from native to 70, and these are represented by small red open symbols. Camera c2 is a Canon PowerShot SD200-2.