Is there an objective test to determine if a picture has been photoshopped?

[raccoon]

Or a video?

[Demit]

1. not at 72dpi. you need access to the original hi-res file to study the pixels.

Otherwise it's a subjective judgment of shadow placement, unnatural hard edges, things like that.

[TechBear_Seattle]

2. You just have to look at it

Almost always, a doctored photo will have irregularities in the background, things like telephone lines that do not line up right or areas where the color is off from the rest of the background. An added element might have shadows and reflections that doesn't line up with the shadows and reflections from other objects, or it might be more in or out of focus compared to other objects at the same distance. And so on.

If the person who altered the photo was sloppy, it will be obvious. Otherwise, you may need to expand the photo to several times it's normal size and inspect it very closely.

[Tandalayo_Scheisskopf]

3. Pixel Deformations are one way.

Look for an "unnatural" line of deformed and jagged pixels around the photo element. Another way is shadows that do not quite match other shadows in a picture.

[mike_c]

4. no-- not if the job was done well-- and I assume you mean...

...a test to determine whether an image was significantly altered, since MOST published images are photoshopped or manipulated through an equivalent program.

A digital image is nothing but an array of numbers representing colors and values. Manipulating the image is simply a matter of changing some of the numbers. Unless you have access to the original image, or unless the manipulation was poorly done, there is no objective way to tell.

[Lerkfish]

5. correct. A well-done job is indistinguishable, because pixel images

are essentially single layer dots on a flat canvas. Anyone can rearrange dots. All it takes is knowhow and enough patience.

[Richard D]

6. That's why . . .

. . . photos are no longer considered evidence in a court setting.

[Lerkfish]

7. can you link the item in question?

that would be easier. however, unless the manipulation is glaringly obvious, its a matter of opinion.
I work in photoshop every day, and I have been sometimes fooled, going from a web image.

[raccoon]

8. There's no particular item, thanks. I was just thinking how pictures could/can

be doctored to deceive people. One poster said that photos aren't used as evidence in court any more.

[Recursion]

9. Yes: does it exist? If so, it has.

I assume by "photoshopped" you mean digitally altered in some way. If that's what you mean, then every picture you can view with a computer is digitally altered, because the compression and rendering process itself is an example of digital alteration and processing.