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Photos that are manipulated usually have telltale signs.
Starting our fourth decade: Al Fasoldt's reviews and commentaries, continuously online for 30 years
How to find out if a photo was manipulated
September 8, 2013
By Al Fasoldt
Copyright © 2013, Al Fasoldt
Copyright © 2013, The Post-Standard
All digital photos, whether from cameras or smart phones, store hidden information about each picture. As we saw last week, this data is part of the "Exif tag." (For more, go to www.technofileonline.com/texts/tec090113.html.)
This data can identify where a photo was taken and what kind of camera took the picture, among many other properties. When you're wondering where you took that seaside photo on your Maine-to-Maryland vacation last year, such information can be very helpful.
But it can also trap a prankster or a criminal. Photos that are manipulated usually have telltale signs both on the photo itself, such as shadows that don't match -- pixel mismatch, in other words -- and in the photo's hidden information, which can indicate whether a picture came straight from the camera or took a detour through Photoshop.
As always, the best way of judging a suspicious photo is by using the thing that sits on top of your neck. If something looks wrong, feels wrong and seems wrong, it's wrong. But for those times when you have a hunch but nothing more, the pros can help you out.
One source of expert analysis is FourMatch, which will sell you Windows or Mac image-analysis software for $890. (They must be kidding, right? No, wrong. Investigators happily pay this sort of fee and pass the cost on to their clients.) But for a much lower cost you can have the company do everything for you, just by uploading up to 30 photos within 30 days. That costs just $20. Go to http://fourmatchdemo.fourandsix.com for more info.
Another source is http://imageedited.com, which provides a basic analysis for free, for any number of photos. A full analysis isn't free, of course; the company will supply a quote.
The difference between basic and full analyses is important. A basic analyses is mostly restricted to Exif information, which may be able to show what steps were taken to alter the original.The "imageedited" site also checks for known "signatures" in pixel patterns as part of its basic service. A full analysis adds all pixel-level changes to its detection methods. If you are checking photos for legal challenges or historical research, you probably should use full analysis.