COLORADO GHOST HUNTERS
DIGITAL IMAGE FORENSICS
by Tad, Colorado Ghost Hunters
October 30, 2007
Using digital imaging has become more widespread, from taking pictures with a digital camera, to using satellite imagery tracking. This increases the need on reliance with digital images for information which in turn increases the need for the authenticity of the image as well. With today's software packages such as Adobe Photoshop, CorelDRAW, and GIMP; the possibilities of image tampering have also become more widespread.
In our field of study pictures are often scrutinized over to decide the authenticity of the image. Those software packages can be used to alter the original image making the process even more difficult. Although there are subtle signs that can be looked at to try and figure if an image is authentic.
PHYSICAL IMPROBABILITIES
Probably the easiest way to tell if a digital image has been tampered with is the physical improbabilities that might exist. Making these kinds of observations requires a bit of patience and careful attention to detail.
One of the things to watch out for are shadows that would look out of place compared to the main light source. Obviously if you have shadows existing in two different directions with only one light source you should be questioning the validity of the digital image.
Repeated images are another dead giveaway, such as with the famous Bush re-election campaign photo that was taken in October of 2004. The photo was digitally enhanced to include extra faces. Careful observation found that some of the faces that were present more than once in the same crowd shot.
Another visual clue is to look at the area in question pixel by pixel. Sometimes a sharp line is produced when one image is pasted on top of another. Combine this observation along with repeated images and you will quickly notice something wrong about the digital image.
DIGITAL IMAGE CHARACTERISTICS
A characteristic of a digital image is the standard size output of the image. Depending on the resolution of the camera the images are created to a specific size. Some of the more common output sizes are 2048x1536 for a 3 mega-pixel camera and 2560x1920 for a 5 mega pixel camera, although there are other size formats.
If you receive a JPEG digital image file from a client that was taken with an Olympus E-1 and the size format is 640x480 this should set off a red flag that the image was tampered with at some point. The standard output size format is 2560x1920, because the Olympus E-1 camera is a 5 mega-pixel camera.
The image type can also lead you to some conclusions. Most digital cameras use EXIF file formats, also known as Exchangeable Image File Formats. These file formats include TIFF and JPEG. Another format that is used usually on digital SLRs and other high end cameras is the RAW file format, which is not standardized.
If your client sends you a file format other than the ones listed above this should set off another red flag. Other file formats could include .GIF, .PNG, .BMP. These file formats are not typical of digital cameras. If the file format is different than what the camera standard outputs you should mark this image as tampered.
Another characteristic is the compression of the file. Although this process is a bit more in-depth. The camera that is used to take a digital image compresses the information through it's own hardware and stores the standard file size and format onto the removable storage media. If the image has been uploaded to a computer and tampered with in anyway the software package will again re-compress the image to save the changes to the digital file.
Researchers at Dartmouth college have developed an algorithm that can be used to check to see if an image has been tampered with in this way. You will need to download Matlab and their algorithm.
Another commercial product is available to check for digital images that have been tampered with, ImageJ. They offer the software for most platforms and supply documentation for the product as well.
CONCLUSION
Unfortunately because of some bad apples we have to investigate a bit deeper than usual when presented with paranormal digital image evidence. By using a checklist and a different perspective on approaching this evidence we can quickly sift through what is not needed. When people contact you with the typical email regarding, "can you look at these pictures for me?" you can quickly dismiss altered images if they are not the original size output of the camera, thus reducing spent time.
Regardless of which side you are approaching ghost hunting, as a client or as a Ghost Hunter, you should demand more from the evidence that you are given. Request the digital camera type and research the camera specification. If the images have been tampered with in any way do yourself a favor and disregard the evidence. Remember this question, "If the evidence has been tampered with, even a bit, what else are am I not seeing?"
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