In western society, a photograph is typically assumed to be an accurate representation of reality.
Most readers seem to understand and expect that widely respected sources of information will adhere to a high standard of photojournalistic ethics. Scientists are usually considered to be respected sources of information and there is the understanding within the scientific community that data must not be inappropriately manipulated or falsified.
However, "tricks" that used to take considerable skill in a darkroom now can be done quite easily by anyone using one of the powerful image editing programs that are available (1).
The most popular software, versatile and of cult status: Photoshop. It started when the Knoll brothers and Adobe struck a deal and PS 1.0 was launched in February 1990. It already included color correction, curves and the clone tool. Every 1-2 years a new version of PS was released, with new tools increasing the range and scope of possibilities to assemble and manipulate images as well as finding ways to disguise the traces. The magnetic lasso came out in 1998, the healing brush was introduced in 2002, with a more refined and powerful version three years later, Cs3 in 2007 offered the refine edge and new blending tools.
It is important to remember that users do not have to be intentionally malicious to alter an image in an unethical manner. Unfortunately, many users are unaware of the issues or the effects of their actions.
The inappropriate manipulation of scientific digital images typically does not arise from an intent to deceive or to obscure information. More often the inappropriate manipulations are simply due to ignorance of basic principles (1).
Modern scientists are under enormous and unceasing pressure to publish. In this environment, to publish quickly and to obtain high-profile results is unfortunately often a lot easier if you don't go entirely by the book. This can easily make the difference between success and failure. At the same time, ever fewer researchers can afford the time to read, or check published work. Researchers are also discouraged from replicating others’ work: replications are notoriously difficult to fund and they don't publish well (2).
Scientific misconduct has raised growing attention lately, including the description of high-profile stories in the popular press. It is a source of concern for scientists, funders and publishers alike.
My background is not in science but in the visual arts. My job is to detect and flag up issues that catch my eye either pre-publication, or to verify allegations of illegitimate image manipulation post-publication. I provide possible explanations for how and why these issues occurred. The final verdict and what action to take as a result is however always a decision that lies with the editors/scientists.
I am also aware of the limitations: Image manipulation is just one aspect of a larger problem, and the issues that are uncovered may only be the notorious tip of the iceberg. It is worth remembering that the lion share of detected image-related problems is due to disorganization, disregard of basic rules and benign errors rather than deliberate scientific misconduct. And well-disguised manipulations performed by an expert user are nearly impossible to detect.
I take this work very seriously. And I know from experience that authors appreciate the service of screening figures prior to publication, which more and more journals are now putting into place. I frequently receive letters from authors expressing gratitude for mistakes and mix-ups caught before publication. Scientists, journals and insitutions can avoid embarrassment and the need to publish a correction later. As Mike Rossner put it: We can do something beyond peer review. Be watchful but not distrustful.
Journals are now frequently approached by whistleblowers pointing out image aberrations in published papers. The COPE Code of Conduct (5) states that editors are ethically obliged to act and pursue alleged cases of misconduct. Countless claims found on post-publication peer review sites like pubpeer are waiting to be investigated and resolved. Careful analysis of image-related problems is a crucial part of this. Institutional investigations may cover multiple papers published over several years, and here patterns of 'bad habits' quite often become apparent. It may sometimes feel like detective work, but I certainly do not consider myself the 'image police'. I'm just 'doing my bit'.
1) Introduction to Image Editing Ethics by Doug Cromey. http://swehsc.pharmacy.arizona.edu/micro/digital-image-ethics
2) A crisis of trust. July 27, 2014 http://blog.pubpeer.com/?p=164
3) Geggie D. J Med Ethics 2001;27:344-6.
4) Godlee F, Wager L BMJ 2012;344:d8357