A friend of ours asked recently whether it would be acceptable to create a composite picture from two separate shots taken at a rally. Neither shot completely captured the tension between demonstrators and police. He argued that a composite image would best reflect the tension at the scene, and wondered whether it would be right to use the composite on the grounds that it conveyed the scene more truthfully than either image separately.

Our answer is no -- not if you are a professional photojournalist.

We rest our argument on two moral concepts that are central to photojournalism: promise-keeping and truth-telling.

Promise-keeping is a form of the moral duty of fidelity. The professional photojournalist has a covenant with the audience. The unwritten agreement arises out of an audience member's need to monitor his or her environment in order to make reasonable decisions.

Because we cannot be in all places at all times, we trust others to watch out for our interests and occasionally to act on our behalf. Police officers monitor traffic and ticket speeders, jurors listen to testimony and determine suspects' guilt or innocence, and journalists monitor newsworthy events around the globe, serving as our eyes and ears.

Part of the journalist's covenant with the audience is the expectation that he or she will witness and record events objectively and accurately.

The second, related moral concept is truth-telling. Philosophers have developed many theories of truth. While they disagree on an exact definition, they agree that most of us, as non-philosophers, subscribe to the correspondence theory of truth, one of the oldest in Western thought. This theory says that something is truthful if it corresponds to facts or reality. Under this theory, for instance, the audience can assume that someone who saw a news photograph of city hall could reasonably expect to identify the building if he or she drove by it.

In addition, the audience understands how a camera works and assumes that the news photograph accurately represents the scene that the photographer witnessed when tripping the shutter. Most people know that the mechanics of photography make the literal correspondence between an event and its photographic representation impossible. However, the audience assumes that the photojournalist acts in good faith to capture a satisfactory rendering of the most important or salient aspects of the scene.

Knowing these assumptions on the part of the audience gives us some idea of how much leeway the photojournalist has when crafting photographs to be published as news.

The covenant with the audience requires that the photojournalist offer the audience the closest depiction possible of the reality he or she witnessed at the time the image was captured.

Deviations from the recorded scene raise questions about the truthfulness of the photograph and the intention of the photojournalist. Some alterations are acceptable. Photos that are too dark might be lightened, for example, and photos containing unnecessary elements may be cropped. But rearranging elements within the picture or combining two shots into a composite betrays the audience's expectations.

The covenant between the photojournalist and the audience has become clearer over time, as certain practices have become entrenched and certain conventions have emerged. The covenant grows stronger each time someone is reprimanded or loses a job for fabricating or materially altering a news photograph.

So, unless a photojournalist discloses the manipulations used to create a composite photo, he or she may be accused of intentionally trying to deceive the audience – and of breaking a promise.