How can I tell definitively if a photo has been retouched?

[swizzy]

This is an odd question but I thought I'd take a shot in the dark by asking.

Is there a link I could be directed to to know whether or not a photo has been in fact photoshopped?

Any help is appreciated

Miss Swizzy

 

[kiddpete]

Short of a physical chain of custody, there is no way to determine if a photo has been altered. That's one of the main objectives of Photoshop. Edit a photo without leaving any evidence of editing.

 

[mscallisto]

If you're "real real" good I can agree with Kiddpete.

If you're "just plain good" or not so good, alterations may be detectable when the image is "blown up" with the magnify tool.

Example:

Your head placed on Ms. Universe's body may look great at nornal viewing size but reveal itself when magnified.
Channel data may also show differences at the points where head joins body, and I'm sure there are other places to look

Whether it was PShop or some other photo altering software may be a bit more challanging to figure out.

 

[maruyama]

Sometimes, a good way to find out whether or not an image has been tampered with is to change the histogram and increase the saturation levels.

Compression errors will become more evident (if any), and changes made to the image may not carry the same compression.

Also, the blacks and white fall offs are very telling.



Ko Maruyama
Free Tutorials

http://homepage.mac.com/komaruyama/Tutorials

http://www.MacAnimationPro.com

 

[GrafxKitten]

You may try throwing a high contrast curve on the image to see any imperfections, if the retouch was not done smoothly you will know right off the bat.

Good Luck


~Kit

 

[mscallisto]

GrafxKitten

"try throwing a high contrast curve on the image "

Sounds interresting but can you explain how to do this?

 

[kiddpete]

I can see finding imperfections in an image file, but swizzy said photo. It's got to be a real clumsy job to spot problems by blowing up, for example, a scanned image of a photo. It seems that one would need a very good printer and a decent size to spot imperfections in the print.

 

[mscallisto]

Wow swizzy did say photo, not image file as I assumed.
My apoligies to kiddpete (who actually read the request)!

 

[GrafxKitten]

Ahh many apologies, in the case of a photo, the job would have to be terrible to be detected. *Photoshop on the brain*
~Kit

mscallisto, I'll be glad to answer you, but I'm off work now! Tomorrow

 

[swizzy]

here is an interesting link I discovered:

http://homepage.mac.com/gapodaca/digital/digital.html

I really found the responses to my question useful here.

Thanks to all who participated. Much obliged

Miss Swizzy