Probably the most robust debate among photojournalists over the past two decades has been over the uses of digital technology and the legitimacy of electronic image manipulation.

Scores of books, articles and symposia have addressed this issue with some clearly positive results for the profession.

But for all of these efforts, there is still far more that photographers and news organizations could be doing to minimize the risks of deception and to maintain credibility with audiences.

This past March, for example, Newsweek was excoriated after it published a cover photo of Martha Stewart without disclosing that the photo was a composite in which Stewart's head had been superimposed on the body of a model.

Newsweek's Assistant Managing Editor Lynn Staley said the magazine clearly made a mistake but that it was an aberration, adding that Newsweek's editors had not "had this particular cigar blow up in our face[s] in the past."

[Actually, Newsweek was blasted in 1997 for giving Bobbi McCaughey - the Iowa mother of septuplets - some digitally-rendered cosmetic dentistry for its cover.]

Aberration or not, the Stewart flap could have easily been avoided if Newsweek had been willing to conspicuously label its cover as a photo illustration.

To its credit, Newsweek has since announced a change of policy that requires bylines to appear on all of its cover photos.

That is a useful first step, but frankly, it is time for Newsweek and every other magazine, newspaper and online publication to start taking a more wide-ranging approach.

After two decades of hand-wringing and after scores of photo-related ethical lapses, there is simply no reason why every publication should not have a policy built around the goal of full disclosure.

A full-disclosure policy would have three key attributes. It would be comprehensive in that every published photo would be labeled to indicate whether, and to what extent, it has been edited. It would be standardized in that it would use a fixed set of symbols or tags to reveal how photos have been modified. And it would be participatory in that it would allow readers to see additional information online, including original versions of altered photos.

If a publication were to commit itself to labeling every published photograph it would immediately distinguish itself from most of its peers, it would establish trust with its readers, and it would guarantee that the Stewart- and McCaughey-type oversights would be, if not extinct, then exceedingly rare.

By being more candid with their readers, full-disclosure publications would also be better shielded against other types of photographic deception.

Two years ago, the Los Angeles Times was burned when it published a photo from Afghanistan by Brian Walski in which elements of two photos were merged to create a more compelling composition. This was a more deliberate and substantive form of deceit and it is the type that is more difficult to prevent. But by creating a culture of openness and requiring that original versions of published images be made available online, it would create a deterrent and increase the chances that purposeful deception would be detected.

Some editors have resisted these kinds of disclosures simply because they add words and clutter to the page. That is an exaggerated concern but in any case one that could be ameliorated by the use of symbols instead of words. Something as discrete as a circle with the letters "PI" inside could be used as a universal symbol that an image is a photo illustration.

Similarly, a circle with the letters "CR" could be used to signal that a photo had been substantially cropped; "CC" could indicate that it had been color corrected (including adjustments to brightness or contrast); "PP" could indicate a posed photo; and "OP" could be used for original, unaltered photos. One could create several more, of course, and in many cases, more than one tag would apply.

Proposals similar to this have been suggested in the past, and some have received the endorsement of major photographic associations, but they have yet to be implemented. In his book, Phototruth or Photofiction?, Thomas H. Wheeler notes that in 1996, New York University's Program on Copyright and New Technologies proposed specific language to be used for various types of photo alterations, and in 1996, NYU's Interactive Telecommunications Program recommended the use of two icons - one for altered photos and one for unaltered photos. Despite some success in Europe, few publications in the United States have taken these steps.

We recognize that there are some concerns. One is that when a photograph is tagged - let's say, because it was color corrected - it might lead readers to dismiss the image entirely instead of acknowledging the truth of the photo's essential message. That would be a problem if a publication only required tags for altered photos. Readers might look at it as a sort of scarlet letter and assume that the photo should not be believed. It would also be a problem for publications that adopted the NYU proposal mentioned earlier, which would flag altered photos but not indicate how they had been modified. A substantive modification would receive the same label as a cosmetic one, yet readers would be prompted to apply the same degree of skepticism.

Under a full-disclosure policy, all photos would carry some kind of tag and it would indicate - at least generally - how the photo had been modified. It would also require that the original photos be posted on the publication's Web site so that interested readers could see even more specifically how a photo had been changed. This would be particularly seamless for online publications, which could turn the tags into hyperlinks that, when clicked, would send the reader directly to the original image along with any photographer or editor comments.

A more powerful criticism of full disclosure is that photographers and editors would treat it as a license to freely manipulate photos, believing that any alterations are justifiable as long as they are disclosed. Many readers would probably continue to interpret photographs at face value, ignoring or dismissing the published tags. So, there is a risk that they could be deceived.

This is a valid concern but it is not a strong argument against disclosure. Full disclosure is not a panacea, nor is it a substitute for careful ethical judgment. Even if every publication adopted this system, there would still be wide variations in the kinds of manipulations that individual publications would tolerate. Full disclosure would not relieve photographers and editors of their core ethical obligations; it would simply give them an additional tool to help establish a more honest and candid relationship with their audiences.

There are risks of deception inherent in the capture, processing and dissemination of images that no photographer or editor can fully avoid. But the best way to ensure the trust of readers is to acknowledge them as essential stakeholders, invite them behind the curtain and conceal from them as little as possible.