How Photoshopped Is That Picture? 226
Freddybear writes "Digital forensics experts at Dartmouth have developed software that can analyze digital photos to rate how drastically they have been altered by digital editing techniques. 'The Dartmouth research, said Seth Matlins, a former talent agent and marketing executive, could be "hugely important" as a tool for objectively measuring the degree to which photos have been altered.'"
reliably? (Score:5, Interesting)
Too bad this requires a "before" picture (Score:5, Interesting)
If it did the analysis using just the "after" image (maybe by looking statistically at ithe ndividual pixel level, I dunno I'm not an image expert) that software would be SO useful for Internet dating sites! ;)
Actually I'm wondering if images CAN be analyzed using statistical data from the individual pixel data to determine things like what camera was used to take the picture, maybe what software was used to edit/convert it (using gamma curves?). Then you could see (maybe) who was posting pictures of themselves from long ago (not like I've ever done that!).
I'd like to run that over (Score:5, Interesting)
My copy of The Commissar Vanishes. Of course, the author presents original photos of Stalin with Large group, smaller group, all by his lonesome at one point and you can examine the technique used for filling in background. Also, photos where someone was added (Comrade is now in favor, include with Stalin at glorious parade!)
As for Photoshop Disasters, there's a website and the checkout aisle for that sort of mental exercise.
Having a little experience here (Score:5, Interesting)
By no means would I consider myself a professional re-touch artist, but I am familiar with the techniques and have produced a few works that were high enough quality for advertising and magazines.
I gotta say, the amount of work that goes in to even the meanest image is staggering. An acquaintance of mine does interior photography for commercial real estate and multi-unit dwellings (apartments, condos, etc.) and while his photography is top notch to begin with, his re-touching is on another plane all together.
He was excited when Photoshop got an upgrade in CS5 to handle more layers because he was routinely bumping up against the limit in CS4. Usually, his work flow consisted of him selecting and making a separate layer for every surface that had a different texture or zone of light, then manually adjusting the levels to bring the brightness and contrast to where he wanted. While tedious and mind-numbing, the over all effect is beautiful true High Dynamic Range images.
Re:Revert? (Score:5, Interesting)
Not likely. When you airbrush, you're destroying the original data. That's why you can detect the change; it no longer has the same fringing around areas of contrast, the noise levels don't quite match, the gradients don't look exactly the same, the reflections of lighting are subtly off, etc. There's nothing to restore because the original information is gone. The best you could do is highlight the areas that were altered. Maybe, if you were lucky, you might be able to approximately reverse a virtual tummy tuck by showing where the moved portions probably were originally, then leaving a gap where content was elided, but that's kind of the exception rather than the rule.
What would be more entertaining would be if someone took this algorithm, then rewrote it (or wrote a parallel successive approximation algorithm to feed into it) so that it generates photos that, although heavily doctored, pass this test. Put another way, this sort of methodology is only effective if the details are kept secret....
some questions (Score:4, Interesting)
Ok,
So what happens if your "I don't want to be called a 'shopper" types simply print out their digital modifications on paper, then scan it again?
That would introduce inkjet pattern/toner dither pattern, and balance the colors in the image.
Would that defeat the genuine check?
If not, how would it react to a scan or photograph of a painting, or line drawing?
Re:reliably? (Score:5, Interesting)
Or just provide better feedback to photo editing programs to create better pictures.
Re:reliably? (Score:5, Interesting)
Actually, conversion is one method of detecting photoshop changes. It's called Image Error Level Analysis.
http://errorlevelanalysis.com/ [errorlevelanalysis.com]
The gist is that every time you save an e.g. JPEG, the quality will get worse. However, the worsening of quality decreases each time it is saved, eventually asymptotically approaching the worst level. Therefore, if you're working on a photoshopped picture, each time you save it the quality of the various parts of the photo will decrease by different amounts. This can be used to identify which pieces of the photo have been modified more recently than others, since they will have a different error level than the pieces that were modified first.
Re:Too bad this requires a "before" picture (Score:4, Interesting)
I used the "levels" tool to prove to someone that a photoshopped version of NASA's famous "Earthlights" picture was NOT a real satellite photo of the big blackout in the northeast a few years ago. Besides recognizing the original picture right away and knowing the story behind it (that it was a composite made of pictures taken over many months), lightening it a whole lot showed which parts were natural (dark but not quite black) and which parts were merely the result of someone using a big, soft-edged brush to put down a lot of pure black.
As the saying goes, I really can tell from some of the pixels, and from having seen quite a few 'shops in my time. :-) (Some of which weren't fake celebrity nudes.)
Pros don't shoot JPEG (Score:5, Interesting)
While interesting, it will not be of much use with professional photographs.
I'm a pro photographer and used to program in Assembly, C and Forth. The way I hide the "life experience" of older women is to use specialized lighting. Small point lights create sharp shadows in skin folds, causing the subject to look extremely old. Very large lights might leave no shadows at all because the light wraps all sides of the skin fold. To achieve this, I use a 7 foot diameter Octobox - a light modifier that creates a huge soft light source. I also use a lens that focuses red light on a different plane than green and blue. The net effect is to soften skin, as blemishes will not be in sharp focus. The camera does not record JPEG, but saves raw sensor data that is later converted into a picture using Photoshop or Lightroom.
Thus as far as software can tell, the JPEG photo produced is the original. There are no re-compression artifacts. In fact, until the RAW sensor data was "de-mosaiced" in Photoshop, one could argue that the picture did not exist as such. And most of the smoothing of the image takes place in the analog world, before a digital file is produced.
I wonder how it deals with in-camera processing (Score:5, Interesting)
I recently got a tiny point-and-shoot camera, a Canon ELPH 300 HS, and I've been participating in CHDK [wikia.com]'s effort to hack it. When we got RAW support working, I learned the camera's lens actually has severe barrel distortion that gets "corrected" in software before saving a JPEG.
Images are "shopped" before they even emerge from the camera these days.
Re:Oh noes: the anti-victoria's secret law! (Score:3, Interesting)
With these images, you start with an attractive model. She has generally maximized her natural beauty (for the sake of argument, in reality, they're quite underweight) and usually enhanced it further through plastic surgery. This is already an unrealistic standard, since most women don't devote their entire lives to their appearance, and aren't in the gifted few that have the potential to be models. But photoshop takes this to an entirely new level.
Symmetry is a universally attractive trait, as it indicates a healthy upbringing, but obviously everyone has some variation. No longer so with photoshop! One side can be mirrored and copied so they're pixel-for-pixel identical. Similarly, airbrushing generates a complexion that is absolutely impossible outside of porcelain dolls. Fat can be redistributed in a way nature would never allow (i.e. beyond plastic surgery), and anthropomorphics are completely lost when body parts are resized. No longer are girls aspiring to overcome mother nature, they're aspiring to something that can never exist in reality!