is picture photomontage or not?

[roberte]

Shiggy,

I imagine one way would be if there are a number of unrelated, seemingly photographic images in the scene that couldn't possibly be there in real life. Although that isn't always a clue as there are many extremely talented 3-d artists that can create very believable scenes.

Robert
www.robertellisonimaging.com

[berniebernie]

Photomontages often give themselves away with lighting (because the angle/sources of light most often differ) but good compositing skills will compensate for that.

You can zoom in a see if you find any stitches/odd patterns and differences in noise (quite hard to imitate respectfully)

You can look at the EXIF data to see if the picture you are seeing is fresh out of the camera (who knows this might be hack-able). You can also check the image properties (right click on the icon, properties>summary>advanced with WinXP) and see if photoshop is the 'creation software'

You can check if the colors have been edited or if there are unusual (unnatural) gaps in the histograms, as shown below (but most photographers do correct their photos prior to publishing them so isn't the best way to figure out how the image has been manipulated)

http://mlkdesign.online.fr/dump/photoedited.jpg

I'm sure there are dozens of other clues to find out the true origin of the picture you are looking at !

mlk

[jeremybirn]

If the Photoshop work were done really well, you might not find any clear evidence in the picture that it's a fake. But there are usually other things you can look at, besides the image itself. Comparing to other pictures is a good idea. For example, if someone has a picture of a city with three buildings bombed out and really only one was bombed, you compare to pictures of the same city from the same angle, and see if some of the buildings have been moved or duplicated around the areas of the supposed bombing. Other times, you find one of the original pictures that people started with in making the composite, and that gives away what they changed. Or you compare pictures of an event with other pictures taken at the same event by other people. Or in a criminal case the police can get a search warren and take the person's computer and back-up disks and look through for evidence of retouching or making fake images.

In the end, forgery in photographs is just like forgery in any other kind of document. If it's a really well made fake, it might be hard to tell by just looking at it, but with some research and verificiation you can still find evidence of whether it's a forgery or not.

-jeremy

[Praedicator]

You can look at the EXIF data to see if the picture you are seeing is fresh out of the camera (who knows this might be hack-able). You can also check the image properties (right click on the icon, properties>summary>advanced with WinXP) and see if photoshop is the 'creation software'
EXIF data is very hackable unfortunately, we see this a lot when someone will post an image from what they claim is a new Digital SLR but in reality they've just modified some of the EXIF data fields for the camera.

The only way I know to verify digital photograph authenticity is with an authentication solution from the manufacturer (Canon makes the Data Verification Kit DVK-E2 and Nikon makes Image Authentication Software which works with Capture NX).

Like Jeremy and others have mentioned a photograph can be a very good fake, but still a fake. Adjusting levels or color balance curves will allow you to detect edges of inserted objects, but that's one of the first things a good fake will cover up ;)

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.