Tag Archives: forensics

Photographic forensics

The FotoForensics site can be a valuable tool in checking the authenticity of an image. It’s easy to alter images with software and try to fool people with them. FotoForensics uses a technique called Error Level Analysis (ELA) to identify suspicious areas and highlight them visually. Playing with it a bit shows me that it takes practice to know what you’re seeing, but it’s worth knowing about if you ever have suspicions about an image.

New Horizons Pluto picture with cartoon PlutoLet’s start with an obvious fake, the iconic New Horizons image of Pluto with the equally iconic Disney dog superimposed on it. The ELA analysis shows a light-colored boundary around most of the cartoon, and the interior has very dark patches. The edge of the dwarf planet has a relatively dim boundary. According to the ELA tutorial, “Similar edges should have similar brightness in the ELA result. All high-contrast edges should look similar to each other, and all low-contrast edges should look similar. With an original photo, low-contrast edges should be almost as bright as high-contrast edges.” So that’s a confirmation that the New Horizons picture has been subtly altered.

Let’s compare that to an analysis of the unaltered image. The “heart” stands out as a dark spot on the ELA image, but its edges aren’t noticeably brighter than the edges of the planet’s (OK, “dwarf planet”) image. The tutorial says that “similar textures should have similar coloring under ELA. Areas with more surface detail, such as a close-up of a basketball, will likely have a higher ELA result than a smooth surface,” so it seems to make sense that the smooth heart (which is something like an ice plain) looks different.
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“Digital forensics”

Now and then I see talk about “digital forensics.” It’s never clear what it’s supposed to mean. “Forensic” means “belonging to, used in, or suitable to courts of judicature or to public discussion and debate.” In popular usage, it’s generally applied to criminal investigations, especially in the phrase “forensic medicine.”

Some activities could be called digital forensics, where digital methods help to resolve contentious issues. For instance, textual analysis might shed light on an author’s identity. Digital techniques can even solve crimes. Too often, though, the term is getting stretched beyond meaningfulness, to the point that routine curation practices are called “forensics.”

No doubt it feels glamorous to think of oneself as the CSI of libraries, but let’s not get carried away with buzzwords.