A few years ago, that would have been true. Today's software for converting scans to PDF documents can be tuned to optimize the conversion a number of different ways. Imagine, for example, that one is trying to scan a brochure which consists mostly of black and white text, but which has a few color photographs thrown in. A few years ago, one would have had to either use a bitonal image for everything (totally wrecking the photographs), use grayscale for everything (making a much bigger file for a given resolution, and still converting the photographs to grayscale), use color for everything (showing everything well, but using an even larger file), or manually specifying various areas to render as bitonal, grayscale, or color. Today, however, one can use software which will attempt to auto-detect different areas of the scan as being color, grayscale, or color, and pick the best rendering for each area. Forensic analysis is pretty well useless on the resulting file, since a lot of details get lost in the conversion.
While one might argue that releasing a file which does not permit forensic analysis should raise suspicions, I'm not sure what sort of forensic analysis one could really do anyway. The Rathergate Memos were produced with equipment totally unlike anything that existed at the time they were supposedly written. I really doubt that would be the case with document reproduced on Obama's BC. Even if one found that a field was typed using a different typewriter from the rest, one could imagine some legitimate ways that could occur. Perhaps someone typed in most of the fields but didn't have one piece of information available; if by the time the information was available someone else was using the typewriter on which most of the information had been typed, someone needing to complete the form could have used a different typewriter for the rest. Unless someone who actually worked in the office at the time could testify that such handling of the form would have been so far outside normal procedure as to be implausible, an irregularity like that would prove nothing.
Then the deniers should be able to easily produce the same exact effects in the same way that Obama's COLB is built. The NRO guy completely failed in doing so. He may be able to fool the uninitiated, but at a closer look his "demonstration" doesn't come close. So far, no one in denier camp as done so.
From another expert who has stepped up.
"Mr. James Colby, who recently performed an analysis aired on a Colorado television station of the image released on April 27, 2011 ...
MR. COLBY: It started when you open the birth certificate in your browser, in Adobe Acrobat. It was a friend of mine who noticed that the text on the birth certificate would flash to white in and out. The reason it was doing that was that there were different layers in the document that caused the layers to flash as it rebuilt the preview layer by layer. So those layers would flash over the top and rebuild that image in that way. From there, you can open it in Adobe Illustrator and see those layers first-hand."
http://www.thepostemail.com/2011/05/09/internet-engineer-obamas-long-form-birth-certificate-a-forgery/
I said very same thing on FR a day or 2 after Obama put out his latest art work. And again, the NRO guy who said that an innocent "optimization" effect would cause the same thing. His demonstration showed a fade in of words as the data was being read during the building of the image from left to right. He didn't use the same type of documents as would be required to convince anyone. If you want to be convincing, you have to do the exactly the same as Obama's COLB PDF and has to be an innocent function as in automatic. And people have to be able to do a peer review on the demonstration so that it can be repeated by others. A step-by-step how-to and it has to be automatic without user manipulation. If you can't do that, you have failed to persuade or prove your point.
Today, however, one can use software which will attempt to auto-detect different areas of the scan as being color, grayscale, or color, and pick the best rendering for each area. Forensic analysis is pretty well useless on the resulting file, since a lot of details get lost in the conversion.
Even if I agreed with you that we get a mosaic of formats, there still should be chromatic aberrations around the black and white text but there is none in Obama's White House COLB. That's another big problem with it. The lack of chromatic aberration around the letters tells us that that Obama's COLB is pasted or layered-in.