Natural images from the birthplace of the human eye

Here we introduce a database of calibrated natural images publicly available through an easy-to-use web interface. Using a Nikon D70 digital SLR camera, we acquired about 5000 six-megapixel images of Okavango Delta of Botswana, a tropical savanna habitat similar to where the human eye is thought to have evolved. Some sequences of images were captured unsystematically while following a baboon troop, while others were designed to vary a single parameter such as aperture, object distance, time of day or position on the horizon. Images are available in the raw RGB format and in grayscale. Images are also available in units relevant to the physiology of human cone photoreceptors, where pixel values represent the expected number of photoisomerizations per second for cones sensitive to long (L), medium (M) and short (S) wavelengths. This database is distributed under a Creative Commons Attribution-Noncommercial Unported license to facilitate research in computer vision, psychophysics of perception, and visual neuroscience.Comment: Submitted to PLoS ON

Facing an Ugly Truth: The Senate’s Report on CIA Torture as Truth-Telling

36 pagesKnown as the “torture report,” the U.S. Senate’s December 2014 report on the CIA’s post-9/11 interrogation program described years of systematic human rights abuses born from an official policy of torture and cruel treatment. The Obama administration ended the program in 2010, marking a transition away from these statesponsored human rights violations. In such a transitional society, it is crucial that the truth be available to the public and to victims to help them move past atrocities; the torture report may be a mechanism for such truth-telling. By considering similar truth-telling reports from other countries as well as the context of the torture report, I assess how this report contributed to transitional justice in four ways: by discovering and acknowledging past abuses, addressing the needs of victims, advancing accountability, and creating institutional reforms and promoting national reconciliation. While not perfect in any respect, the report has affected the way Americans view the CIA program, contributed to legislation banning torture, and created consequences for some of the program’s architects

Cone Parameters for LMS Images.

<p>CVRL database is accessible at <a href="http://www.cvrl.org/" target="_blank">http://www.cvrl.org/</a>.</p

Example images from the Botswana dataset.

<p><b>A–D</b>) Some natural scenes from various albums, including a tree, grass and bushes environment, the horizon with a large amount of sky, and closeups of the ground; the last image is from the image set containing a ruler than can be used to infer the absolute scale of objects. <b>E–F</b>) The distributions of L (red), M (green) and S (blue) channel intensities across the image for images A) and B), respectively. The large sky coverage in B) causes a peak in the S channel at high values. The horizontal axis is log base 10 of pigment photoisomerizations per cone per second. <b>G–H</b>) Grayscale images showing log luminance corresponding to the images in C) and D), respectively.</p

Camera spatial MTF.

<p>Estimated MTF is plotted as a function of spatial frequency for the red, green, and blue image planes (shown in corresponding colors). Solid lines show empirical fits to , where for all , is set to 1 and where any fit values greater than 1 were also set to 1. The fit parameters are for red channel, for green channel, and for blue channel. MTF values at cycles/pixel (empty plot symbols) systematically deviated from the rest and were excluded from the fit.</p

Pairwise correlations in natural scenes.

<p>We analyzed 23 images of the same grass scrub scene, taken from different distances (black – smallest distance, red – largest distance). For every image, we computed the pixel-to-pixel correlation function in the luminance channel, and normalized all correlation functions to be 1 at pixels. For largest distances, pixels, the correlations decay to zero. The decay is faster in images taken from afar (redder lines, the largest distance image shown as an inset in the lower left corner), than in images taken close up (darker lines, the smallest distance image shown as an inset in the upper right corner). All images contain a green ruler that facilitates the absolute scale determination; for this analysis, we exclude the lower quarter of the image so that the region containing the ruler is not included in the sampling.</p

Linearity of the camera in ISO setting.

<p>The mean raw RGB response of the three color channels (red, green, blue; shown in corresponding colors) is plotted against the ISO setting after dark subtraction, for two values of exposure time (solid line, circles = ; dashed line, squares = ), and aperture. The lines are linear regressions through non-saturated data points (solid squares or circles; raw dark subtracted values between 50 and 16100); the slopes are 0.99 (R), 0.98 (G), 0.99 (B) for exposure and 1.03, 1.02, 1.04 for exposure. The camera saturated in the red channel at longer exposure; the corresponding data points (empty red circles) are not included into the linear fit.</p

Spectral response of the camera.

<p><b>A</b>) The spectral sensitivity curves plotted here convert spectral radiance into standardized camera RGB values. <b>B</b>) The LMS cone fundamentals <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020409#pone.0020409-CIE1" target="_blank">[29]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020409#pone.0020409-Sharpe1" target="_blank">[45]</a> for L (red), M (green) and S (blue) cones. Note that the fundamentals are normalized to have a maximum of 1. <b>C</b>) A linear transformation can be found that transforms R,G,B readings from the camera with sensitivities plotted in (A) into reconstructed fundamentals L'M'S' shown here, such that L'M'S' fundamentals are as close as possible (in mean-squared-error sense) to the true LMS fundamentals shown in (B).</p