Personal computers can help you create new realities. This can be magical, but it can also be dangerous.

One of the ways that PCs, Macs, and digital devices do this is through computer-aided photography, also called digital imaging.

You start with a facsimile of reality, typically with a photo that you’ve taken with a stand-alone digital camera or camera that’s part of your phone. Then you work on the photo, either on your own equipment or over the cloud.

Image editing programs let you enhance, correct, or otherwise alter photos. On the other hand, in changing reality you can sometimes create a false one.

One of the more famous and embarrassing examples of this was during the O.J. Simpson affair 20 years ago when both Time and Newsweek used the same cover photo of Simpson, an arrest mugshot. But Time darkened Simpson’s skin, which may have been done to make him look more sinister or at least more dramatic. In the eyes of many, this was a cheap attempt at digital sensationalizing.

On an everyday basis, those working with photos in ad agencies or other business settings make people look too good, with perfect white teeth and sparkling eyes, having no hair out of place, and without a wrinkle, freckle, mole, or pimple.

Lots of different tools exist for this kind of work, for pros and amateurs. The leading high-end program is Adobe Photoshop and has been since it was released in 1990. The program has had such a cultural impact that many people now use the neologism “photoshop” in a generic sense to mean digitally enhance a photo regardless of what program you use.

Though impressively versatile, Photoshop remains pricey. A more appropriate program for nonprofessional users is Photoshop Elements. Another popular program is Corel Paint Shop Pro. Paint.NET and Picasa are free basic photo editing programs.

Regardless of which program you use, the single most important thing to remember is to avoid overdoing it. Retouching works best when people looking at a photo don’t know what you’ve done to it. That’s your best compliment. A retouched photo shouldn’t look retouched.

Retouching in particular is most beneficial when you’ve made a mistake in taking the photo involving the lighting, the camera settings, or the way you’ve composed the shot.

Perhaps the photo exhibits a false orange cast, depicts a tree in the background that looks as if it’s growing out of your subject’s head, or shows a distracting trash can in an otherwise beautiful vacation picture. Perhaps your subject’s wrinkles look harsher or teeth yellower than in reality.

It’s always best to avoid mistakes in the first place. To prevent off-color photos when shooting inside, change your digital camera’s “white balance” setting, use special “daylight-balanced” lightbulbs, or place your subject by a window.

To prevent the devilish “red eye” problem if you use a flash, use your camera’s red-eye setting, turn up the lights, or tape a small piece of tracing paper over the flash to diffuse its light.

When composing a shot, fill the camera’s LCD screen or viewfinder with what you want to appear in your photo by moving close to your subject or using the camera’s zoom. Avoid situations where objects such as telephone poles are directly behind your subject’s head.

Unless you have a high-end dedicated digital camera, avoid subjects such as trees that consist of intricate details. In general, avoid background that’s overly cluttered or distracting. People and other subjects that clearly stand out from their backgrounds work best with digital cameras.

Image editing programs not only let you correct mistakes, they also let you get creative. You can combine elements from different shots to construct a montage or impart jazzy special effects, including those that make a photo look like a watercolor or oil painting.

Image editors often provide lots of tools, and one of the tricky things in using them is choosing the most appropriate tool. Practice makes perfect.

More information about this issue is out there, online and in print.

Photo Fakery: A History of Deception and Manipulation is a book by former CIA agent Dino A. Brugioni that explores how this has been done in the past.

A Brief History of Photo Fakery is an online New York Times slideshow with famous historical examples.

No-Filter is a new Facebook community created by my 19-year-old daughter that explores how young people sometimes feel pressured into unrealistically improving their appearance in online photos.