I came across a website a few years back that I can no longer locate. My google-fu might be rusty or the site may have been taken down since then. It was called "Project Hawkeye" and was made by a guy whos theory was that ghosts might be more visible in photographs on the low-level ultraviolet spectrum. He said that most modern cameras are designed to filter out most of the ultraviolet light and that could be why ghosts dont always show up on film even if you were looking right at one at the time you took the photograph. You can buy special ultraviolet camera lenses but they aren't cheap ($3000 or more). So his solution was to use an array of old cameras from the 40's and 50's that didnt have any kind of filters. If I remember correctly he was using a set of three brownie hawkeye cameras. http://www.brownie-camera.com/27.shtml He was using three because they dont have a very high resolution individually. He was trying to set them up on a tripod at certain distances apart so they could be combined into one photo more easily. Last time I checked it a few years ago he was still in the process of putting it together. So the results are still unknown. Has anyone heard of this site or theory before?