Ah. That's just normal stuff and depends on the scanner settings and how much JPEG compression is used. Has absolutely nothing to do with whether or not it's a forgery.
I laser printed a "blank" certificate on a sheet of solid green sheet of paper. Then I scanned one of the iterations of "BIRTH." Here's a zoomed image of what the scan looks like straight from the scanner, before any JPEG compression has been applied:
You'll notice that even though the actual page I scanned was only solid green paper and black printer toner, there are quite a lot of full white and nearly full white pixels surrounding the text.
That's due to the scanner.
Now here's a zoomed image of the same scan after it's been mangled by JPEG processing:
Here you can see the weird pixelation patterns as a result. You'll also notice that whereas there were some decidedly green pixels between the B and the I and the I and the R in the raw scan, now they're mostly colorless as a result of JPEG processing.
JPEG is what's called a "lossy" compression scheme, as opposed to "lossless" compression schemes.
Lossy compression schemes, in addition to making the file size smaller, actually removes information from the original image. It does this using algorithms based on human visual perception, so that the resulting images still look "ok" to the eye. This allows the file sizes to be smaller than they could be using a lossless scheme.
MPEG is an example of a lossy compression scheme for audio. And like JPEG, it also removes information from the original audio file using algorithms based on psychoacoustics in order to give acceptable sound.
The reason the artifacts in the Obama image seem to be of a lighter shade is because it was scanned using different scanner settings, namely brightness and contrast.
If you notice, the space between the green "rods" and "dots" that make up the background pattern in the Obama scan is mostly white. Whereas in the Michele scan, it's all just a lighter shade of green.
This will affect what the result will look like once JPEG processing has been done. Also, JPEG allows for different levels of quality so you'll get different artifacts even on the same raw image depending on what the quality level was set at.
So again, none of this has anything to do with whether or not the document was forged. In fact, just the opposite. The forging of a document WOULDN'T produce these artifacts.
Here's a "forged" Obama certificate I made a while back just for grins:
Polarik claims that the paucity of colored pixels BETWEEN the letters is a sure sign of a forgery. However if you look at this image, you'll see that there is no lack of colored pixels between letters, except where there would have been no green in the first place.
That's because the text was never printed on paper and scanned (which as I illustrated above produces full white pixels around the text). The text in this image was produced entirely digitally and the image simply saved out as a JPEG.
I've said it before and I'll say it again. Polarik simply has absolutely no business talking about imaging and graphics. He has never demonstrated that he has any knowledge or experience in the field. He just looks at something he doesn't understand and then makes up some story about it being proof that the image is a forgery or has been altered.