There is often an obvious difference between photos and illustrations. What may not be as obvious is knowing when it's best to use a photograph versus an illustration in your respective project. The following will provide a solid foundation of the whens and whys of each visual format.

Photographs are more grounded in reality than illustrations. To depict something in a literal way, photos are the clear choice, especially if you're selling a specific physical product like food or clothing. Large corporations often stick with photos to avoid appearing surreal or provocative. In industries where competence and professionalism are critical -- like air travel, corporate security, or oil drilling -- you're much more likely to see photos at work.

This is not to imply that photos are only good for detailing visual description. Many photographs are deliberately unrealistic, through creative composition, optical illusion, and digital manipulation. But this taps into the ambiguity of pure art, and is best used to convey a theme or abstract idea, not a specific product. For example, the above image contains elements of photography, but its "photo-illustration" style obviously works best as a metaphor. (Unless your company sells seaworthy armchairs.)

This very attribute of photography is where illustrations find their power. Illustrations can freely ignore reality to express themes and concepts, and engage the imagination in fun, weird, even impossible ways. For example, the content of the below illustration is difficult, if not impossible, to achieve in a straight-up photograph.

Illustrations come in countless styles and forms that can be used to your advantage. Suppose, for example, you need an image of a bear. Take a look at this collection of bear illustrations. From angelic to aggressive, this near-infinite stylistic variety of illustrations assists you in finding the appropriate image for your specific strategic needs. That's another way to navigate the larger question of photo vs. illustration; use your overall marketing strategy as the basis of your decision, and not your personal taste. What you happen to like may simply be wrong for the larger, objective goals of your project.

So, when in doubt, ask yourself the following kinds of questions:

Q. Are you selling a specific product? A. Use a photo to display it clearly.

Q. Are you selling something less tangible? A. Try an illustration to capture its theme.

Q. What is the age range of your target audience? A. Younger people may be more receptive to the sly whimsy of a fun illustration, while older people may prefer the trustworthy vibe of a sensible photo.

Q. Is your business an underdog, compared to the market leaders who use the same kind of photos? A. Try an illustrated style to shake things up and set you apart.

Q. Are you a large firm that needs to play it safe? A. Photos may be best.

This is not an exact science, of course, and sometimes it pays off to gamble and defy convention. Just make sure that whether you put a photo or an illustration to work, you've done your best to understand how your audience may react. It can really raise the odds that your project will hit the home run you need.

Brian Goff is a graphic designer and illustrator who is passionate about branding, creative strategy, and entrepreneurship. You can view his work, and get in touch with him at his online portfolio, www.briangoff.com. You can also follow him on Twitter at @briangoff.