Photographs capture a moment in time. 

Photos are generally regarded as "factual," as opposed to a drawing or painting, which would be the artist's interpretation.  Photos tend to be trusted more, because they accurately depict what was in front of the camera at the moment the picture was taken. 

At least, photographs are supposed to be accurate.  How easy is it to edit a photo so that it shows something different than what really happened? 

The concept of photo editing is almost as old as photography itself.  The first photographic images were recorded in the 1820s, and one of the first widely known edited photos was a portrait of Abraham Lincoln.  Sometime in the 1860s, someone took a standing portrait of Southern Congressman John Calhoun, pasted in Lincoln's face from the portrait for the five dollar bill, and created a historic photo of Lincoln on the spot. 

Even an action as simple and innocent as cropping the picture can be controversial.  Imagine a scene of the wreckage left by a tornado.  If the photographer cropped out all of the damage, and focused instead on a single building that somehow survived, it would appear that the tornado hadn't damaged very much at all. 

In today's world of digital photography, some photo editing is necessary on nearly every picture.  Digital cameras have to "guess" at the proper color, contrast, and shading of the pictures they take, and proper use of photo editing tools can correct or even enhance the camera's guesswork. 

At the same time, digital photographers must keep in mind that photography--especially journalistic photography--is meant to be a record of a moment in time, and not an artistic recreation of what the photographer wants his audience to see.  While editing photographs has become quicker and easier, the temptation to alter the photographs has risen as well.